Tramadol is a centrally acting opioid analgesic which is increasingly used in Sweden. Dependence, abuse and withdrawal has been reported in patients treated with tramadol. The incidence of these adverse effects is considered to be low. Patients with a history of substance abuse might be at higher risk than others to develop dependence. The number of forged tramadol prescriptions uncovered in Swedish pharmacies was relatively low in 2001, compared to those of prophoxyphene and codeine, but increasing.