The authors are herewith reporting the results of an immunological screening performed on 15 drug addicts presenting serological positivity for anti HTLV III (Elisa and WB). The study has been carried out determining populations and subpopulations of lymphocytes (T3, T4, T8 and T4/T8) and performing cutaneus tests with multiple antigens (Tetanus--Candida--Diphtheria--Proteus--Streptococcus and Tricophyton). The results achieved by mean of the above mentioned tests seem to indicate the presence of an immunodeficit hitting mainly the cell-mediated immunity in all the patients examined.