AbstractNoting that the inducibility of samples tested with the SOS Chromotest increased with increasing colour development time, a slightly modified Chromotest procedure was developed and applied to six sediment samples from Prince Edward Island. The samples tested by this newly developed short‐term genotoxicity test showed weak inducibility expressed by the SOSIP—SOS Inducing Potency. Five of the six samples were activated by the addition of S‐9 fraction, commonly used with the Ames/Microsome test. Only one of the samples showed toxic activity by the Microtox