Four hundred fifteen shellfish seawater samples from approved, conditionally approved, and restricted areas along the coastlines of Connecticut, Massachusetts, and Maine were tested in duplicate to compare results obtained with A-1 medium (AOAC official method no. 978.23) and those obtained with A-1 medium without salicin. Four laboratories used five sets of most probable number procedures to perform the analyses. No statistically significant differences between the two media were found with the t test, the F test, or the analysis of variance.