Concentration of neopterin (NPT) was measured in 3-6 months intervals in the serum of HIV-infected drug users taking continuously intravenous drugs and those who stopped the habit (MONAR, ZOZ). After 6-12 months of observation the mean NPT concentration was higher in the active drug users what was statistically essential. The outcome of our study indicates that current state of the patient concerning taking of drugs must be taken under consideration when NPT concentration is assessed as marker of progression of HIV disease.