The present study was undertaken to investigate the dental health of a group of parenteral drug addicts. The study population comprised 134 persons with a mean age of 25 yr (min. 18, max. 37) examined in 1977-81. Mean DMFT was 18.3 and mean DMFS was 50.2, approximately twice as much as found in comparable age groups in Denmark. Even free smooth surfaces were often involved. The oral hygiene was measured by the use of the Visible Plaque Index (VPI) and the Bleeding Index (BI). Both indices were high, mean VPI = 77.4 and mean BI = 71.3. 12-40% of the teeth selected had a loss of periodontal attachment of more than 4 mm. It is suggested that not only drug abuse, but also factors like low social status, low education and different barriers towards receiving dental treatment should be considered in a multifactorial cause-effect relationship. The effect of offering a free dental care system for this high-risk group will be dealt with in another paper.