More than 400 hazardous waste contamination sites exist in California's Silicon Valley. Zealous enforcement of deanup laws and the threat of litigation have meant that toxic con tamination can drastically affect market values of property. Uability insurance to cover cleanup costs is virtually unavail able. However, Silicon Valley's competitive commerdal/ industrial real estate market has forced buyers and sellers to allocate the risks posed by contaminated properties instead of immediately terminating transactions. Nine case studies in this article illustrate that many contaminated properties in Silicon Valley continue to sell at near-market prices. Such land transfers are now routinely subject to an array of mech anisms designed to internalize the costs of cleanup, includ ing in-depth environmental risk assessments, detailed pur chase agreements, and long escrow periods during which cleanup can begin.