The frequency of successful analgesia and the frequency of general side effects during dental treatment of previous and present drug addicts were investigated in a controlled clinical study. A solution of xylocaine/adrenaline (20 mg/ml + 12.5 micrograms/ml) was used in a dose of 1.5 ml for 88 mandibular blocks in order to test the frequency of analgesia. Successful analgesia was recorded only if the patient experienced no pain in the operative area. The number of side effects such as unrest, anxiety, sweating, pallor and palpitation was recorded during another part of the study. The frequency of successful analgesia was lower among the previous and present drug abusers compared to the control group and the difference was statistically significant. A statistically higher number of side effects was recorded in both experimental groups. The need for a higher dosage of local analgesic and the higher number of side effects is attributed to the fear and anxiety among this particular group of patients. In the light of these findings the significance for the management of drug addicts during dental treatment is discussed.