Exhibit 99.1

Press						II-VI Incorporated
Release						375 Saxonburg Boulevard
						Saxonburg, Pennsylvania 16056
						Telephone (724) 352-4455

II-VI INCORPORATED DECLARES

TWO-FOR-ONE COMMON STOCK SPLIT

PITTSBURGH, PA, May 17, 2011 — II-VI Incorporated (NASDAQ: IIVI) announced today that its Board of Directors authorized a two-for-one stock split of the Company’s Common Stock in the form of a 100% common stock dividend. Shareholders of record as of the close of business on June 3, 2011 will receive one additional share of II-VI common stock for each share then owned. II-VI expects that its transfer agent, American Stock Transfer and Trust Company, will distribute the additional shares on or about June 24, 2011. There are currently approximately 31.3 million shares of II-VI common stock outstanding. Upon completion of the stock split, there will be approximately 62.6 million common shares outstanding.

Francis J. Kramer, president and chief executive officer of II-VI Incorporated stated, “Today’s stock split reflects our continued commitment to building value for our shareholders and demonstrates the confidence of our Board of Directors and management in both the fundamentals and growth potential of our business. In addition, the split is intended to further improve our liquidity and to make our shares more accessible to institutional and individual shareholders.”

About II-VI Incorporated

II-VI Incorporated, the worldwide leader in crystal growth technology, is a vertically-integrated manufacturing company that creates and markets products for diversified markets including industrial manufacturing, military and aerospace, high-power electronics and telecommunications, and thermoelectronics applications. Headquartered in Saxonburg, Pennsylvania, with manufacturing, sales, and distribution facilities worldwide, the Company produces numerous crystalline compounds including zinc selenide for infrared laser optics, silicon carbide for high-power electronic and microwave applications, and bismuth telluride for thermoelectric coolers.

In the Company’s infrared optics business, II-VI Infrared manufactures optical and opto-electronic components for industrial laser and thermal imaging systems and HIGHYAG Lasertechnologie GmbH (HIGHYAG) manufactures fiber-delivered beam delivery systems and processing tools for industrial lasers. In the Company’s near-infrared optics business, VLOC manufactures near-infrared and visible light products for industrial, scientific, military and medical instruments and laser gain materials and products for solid-state yttrium garnet (YAG) and yttrium flouride (YLF) lasers. Photop Technologies, Inc. (Photop) manufactures crystal materials, optics, microchip lasers and opto-electronic modules for use in optical communication networks and other

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II-VI Incorporated

May 17, 2011

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diverse consumer and commercial applications. In the Company’s military & materials business, Exotic Electro-Optics (EEO) manufactures infrared products for military applications, Pacific Rare Specialty Metals & Chemicals (PRM) produces and refines selenium and tellurium materials and Max Levy Autograph, Inc. (MLA) manufactures micro-fine conductive mesh patterns for optical, mechanical and ceramic components for applications such as circuitry, metrology standards, targeting calibration and suppression of Electro-Magnetic Interference. In the Company’s Compound Semiconductor Group, the Wide Bandgap Materials (WBG) group manufactures and markets single crystal silicon carbide substrates for use in the solid-state lighting, wireless infrastructure, RF electronics and power switching industries; Marlow Industries, Inc. (Marlow) designs and manufactures thermoelectric cooling and power generation solutions for use in defense, space, photonics, telecommunications, medical, consumer and industrial markets; and the Worldwide Materials Group (WMG) provides expertise in materials development, process development and manufacturing scale up.

This press release contains forward-looking statements based on certain assumptions and contingencies that involve risks and uncertainties. The forward-looking statements are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and relate to the Company’s performance on a going-forward basis. The forward-looking statements in this press release involve risks and uncertainties, which could cause actual results, performance or trends to differ materially from those expressed in the forward-looking statements herein or in previous disclosures. The Company believes that all forward-looking statements made by it have a reasonable basis, but there can be no assurance that management’s expectations, beliefs or projections as expressed in the forward-looking statements will actually occur or prove to be correct. In addition to general industry and global economic conditions, factors that could cause actual results to differ materially from those discussed in the forward-looking statements in this press release include, but are not limited to: (i) the failure of any one or more of the assumptions stated above to prove to be correct; (ii) the risks relating to forward-looking statements and other “Risk Factors” discussed in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2010; (iii) the purchasing patterns from customers and end-users; (iv) the timely release of new products, and acceptance of such new products by the market; (v) the introduction of new products by competitors and other competitive responses; and/or (vi) the Company’s ability to devise and execute strategies to respond to market conditions.

CONTACT: Craig A. Creaturo, Chief Financial Officer and Treasurer of II-VI Incorporated, 724-352-4455, or e-mail, ccreaturo@ii-vi.com.

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