This study determined the prevalence of personality disorders among clients in treatment for addiction; this prevalence was compared with those found in similar studies and in clinical samples of individuals suffering from other Axis I disorders. Our sample comprised 255 subjects. The first edition of the Millon Clinical Multiaxial Inventory (MCMI) was used. Only 11.8% of the subjects did not score over 84 on any of the 11 Axis II scales. Over one-half had a score of 84 or higher on the passive-aggressive and dependent-personality scales. The mean number of scales in the 84+ category was 2.68. Comparisons show that this sample was more severe in most cases.