The past few years have seen increased interest in the determination of bacteriological quality of shellfish as received at the market. Some agencies established either official or tentative working standards by which they could at least classify the product as received. Possibly the most notable is the classification system established by Canada in 1951, which groups the shellfish into three classes, Acceptable, Acceptable on Condition, and Rejectable, and allows judgment whether a product should enter or be tolerated in the consuming area. Because of the success of Canada with this scheme, the method was accepted in principle at the Shellfish Sanitation Workshop, with the modification of extending the coliform MPN limit in the Acceptable class from 2,400 to 16,000. The bacteriological criteria established at the 1956 Shellfish Sanitation Workshop is summarized.