The mission tiles are laid in a regular pattern, and complement the missionesque shaped gables at each end of the building. The gables are coped in stucco. Aside from the simple mahogany wainscot paneling and casework that trim the front reception office, the building's interiors are uniformly spartan. Typical of this simplicity is the main staircase to the second floor labs, which is a study in utilitarian design with painted pipe rails. The building plan was laid out on an informal grid of interconnecting rooms.
Finishes are clinically white, and none of the rooms has changed markedly over the years.
Minor additions of suspended ceilings accommodated the installation of fluorescent fixtures to increase light levels at lab counters and work stations. The Twining Laboratories Building is significant as a Depression-era work of regionally important architect Charles E. Butner . It is a solid example of a small commercial office designed in a variation of the Mediterranean Revival style not otherwise seen in downtown Fresno. Twining was born in Croton, Ohio, and studied chemistry at Denison University. He attended medical school in Columbus, Ohio, after which he entered the pharmaceutical business before migrating to California in 1897.