Oleylamine was tested for mutagenicity in vitro in L5178Y TK+/- mouse lymphoma cells, both in the presence and absence of Aroclor-induced rat liver S-9 metabolic activation. Based on preliminary determinations of cytotoxicity, the compound was tested in 3 trials without activation at concentrations ranging from 0.13-0.32, 0.13-1.8, and 0.2-1.0 nl/ml culture medium, and in 3 trials with activation, at 1.3- 10.0, 1.3-13, and 1.5-11 nl/ml. Cell survival without activation ranged from 75-99, 3-110, and 6-109%, for the first, second, and third trials, respectively. Cell survival with activation ranged from 6-106, 13-107,and 2-115%,for the first, second, and third trials, respectively. The treatment did not increase the frequency of forward mutations at the thymidine kinase locus, indicating that the test compound was not mutagenic in mouse lymphoma cells under the conditions of this assay.