With the support of the Swedish National Institute of Health a national information service was started in 1993 aiming to capture the abuse of doping agents in the general public. It was organized as a telephone service, called the Anti-Doping Hot-Line, from our department and managed by trained nurses co-operating with clinical pharmacologists. Important information collected about all callers (anonymous) was: date of call, its origin, category of caller, doping experience and main question being asked. Abusers were asked about their age, sex, affiliation, abused drug(s), duration of abuse, habit of administration and adverse reactions (ADRs). Between October 1993 and December 2000 25,835 calls were received with a peak during spring and autumn. Most calls (12,400) came from non-abusers, 60% being males. Callers connected with gyms represented the largest group (30%). Most calls about specific drugs concerned anabolic androgenic steroids (AAS). Other drugs or products included ephedrine, clenbuterol and creatine. The most commonly abused anabolic steroids were testosterone, nandrolone-decanoate, methandienone and stanozolol. The ten most commonly reported ADRs of AAS were aggressiveness (835), depression (829), acne (770), gynecomastia (637), anxiousness (637), potency problems (413), testicular atrophy (404), sleep disorders (328), fluid retention (318) and mood disturbances (302). Female side effects included menstruation disturbances, hair growth in the face, lower voice and enlarged clitoris. During the period 1996-200, totally 4339 persons reported about 10,800 side effects. This figure should be compared with the very low number of ADRs (27) reported by prescribers to the Swedish ADR committee during the same period. Abuse of doping agents appears to be a new public health problem that needs detection, medical care and prevention.