As a third Market Surveillance Study of Suspected Illegal Products (MSSIP003), the OMCL Network decided to carry out a retrospective exercise on illegal anabolic steroids. These products are regularly tested by the OMCLs on behalf of their Competent Authorities and upon request by police, customs or other enforcement groups. The intention was to collect and compile pre-existing data for the study and to provide a picture of the situation at a defined point in time, which is nevertheless likely to be representative of the current market situation.