This article argues that labor activists initiated Silicon Valley's anti-toxics movement and were the driving force behind environmental remediation in the region in the first half of the 1980s. In order to unionize semiconductor plants, activists associated with SCCOSH and United Electrical, Radio, and Machine Workers, a left-wing union, attacked corporate negligence regarding worker safety and health. SCCOSH later allied itself with the Central Labor Council of Santa Clara County to push for the cleanup of aquifers contaminated by the semiconductor industry. The activists ultimately failed to organize Silicon Valley, but their campaigns led to a revolution in safety among microelectronics firms and to large-scale remediation efforts conducted under the EPA's Superfund program.