[en] This document was developed to provide the personnel working in the Environmental Sciences Division's Toxicology Laboratory with documented methods for conducting toxicity tests. The document consists of two parts. The first part includes the standard operating procedures (SOPs) that are used by the laboratory in conducting toxicity tests. The second part includes reference procedures from the US Environmental Protection Agency document entitled Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, upon which the Toxicology Laboratory's SOPs are based. Five of the SOPs include procedures for preparing Ceriodaphnia survival and reproduction test. These SOPs include procedures for preparing Ceriodaphnia food (SOP-3), maintaining Ceriodaphnia cultures (SOP-4), conducting the toxicity test (SOP-13), analyzing the test data (SOP-13), and conducting a Ceriodaphnia reference test (SOP-15). Five additional SOPs relate specifically to the fathead minnow (Pimephales promelas) larval survival and growth test: methods for preparing fathead minnow larvae food (SOP-5), maintaining fathead minnow cultures (SOP-6), conducting the toxicity test (SOP-9), analyzing the test data (SOP-12), and conducting a fathead minnow reference test (DOP-14). The six remaining SOPs describe methods that are used with either or both tests: preparation of control/dilution water (SOP-1), washing of glassware (SOP-2), collection and handling of samples (SOP-7), preparation of samples (SOP-8), performance of chemical analyses (SOP-11), and data logging and care of technical notebooks (SOP-16)