A shake-flask screening test was designed to rapidly evaluate the relative degradation rates of a wide spectrum of chemicals, each compared to methyl parathion. Test chemicals evaluated were bolero, bravo, dibutylphthalate, dimilin, dursban, endosulfan, hoelon, pentachlorobenzene, phorate, and trifluralin. Diverse regimes of salinity, pH, TOC, and microbial biomass were encountered across space and time. The experimental design for the screening test embodies four treatments: active sediment, sterile sediment, active water and sterile water. Decay curves were produced and rate constants and half-life values determined. Half-life values for the 10 chemicals evaluated varied substantially with time and geographic sampling site. In active systems, 8 of the 10 chemicals degraded more rapidly than methyl parathion. Nine dibutylphthalate screens were run involving six geographic sites. Disappearance was quite rapid in active treatments in all screens. Disappearance curves describing DBP abatement either: (1) appeared to be substrate dependent with the rate of degradation decreasing as DBP was depleted; (2) appeared independent of substrate concentration; or (3) reflected a marked increase in degradation rate during the screening period.