Thomas A. Tardio is stepping down as chairman and chief executive officer of PR-marketing agency Rogers & Cowan after 27 years at the company.

Tardio, 63, is moving on to a new post in Silicon Valley as chairman of social networking concern Socialtext, starting July 5. In the interim, he’ll move into the newly created role of chairman emeritus at Rogers & Cowan and work with Octagon Entertainment CEO Rick Dudley on the search and interview process for a successor.

He informed his Rogers & Cowan colleagues of the move on Sunday. Paul Bloch, one of the firm’s original partners, remains co-chairman.

Tardio joined the agency in 1988 as chief financial officer and was promoted to the post of executive vice president and head of its domestic and international entertainment operations. He replaced Richard Taylor as CEO in 1991.

Tardio has overseen the agency’s expansion beyond its core business of representation of high-profile clients in the entertainment industry and into the role of an integrated marketing firm capitalizing on consumer goods companies’ desire to reach targeted audiences.

During his tenure, Rogers & Cowan expanded into markets such as product placement, film festivals, cable and network television programming, album launches, concert tours, fashion designers and collections, awards show campaigns, digital entertainment, streaming media and consumer electronic devices. Clients have included Microsoft, Ford, Texas Instruments, Coca-Cola, Walden Media, Fox Consumer Products, Amazon Studios, The Recording Academy’s Grammys and EA Sports.

Shandwick PLC  purchased Rogers & Cowan in 1987. Shandwick was bought by the Interpublic Group of Companies in 1998. Sports-entertainment marketing concern Octogan Entertainment is part of Interpublic.

Prior to Rogers & Cowan, Tardio worked for a decade at Columbia Pictures Industries in various posts in the motion  picture, TV, corporate finance and operations areas and played a major role in development of the studio’s strategic plans.

Socialtext specializes in business-to-business social networking products. The 13-year-old company, located in Palo Alto, is a subsidiary of Peoplefluent and a Bedford Funding portfolio company.