The monitoring system PHAR-MON (formerly: ebis-med) documents the misuse of pharmaceuticals in addiction counseling centres as an early warning system. It is described as a diagnostic instrument according to its aims and tasks, implementation and assessing procedures and is evaluated according to the main quality criteria of diagnostic instruments. In addition, selected results are reported about the misuse of medicaments in the year 2004. In analogy to diagnostic instruments, the main quality criteria objectivity, reliability and validity are applied to evaluate PHAR-MON, they are extended, however, by the validity of the sample of reference outpatient centers. Statistical methods for proving results are applied and discussed concerning their appropriateness for cross-sectional and longitudinal analyses of PHAR-MON data. The selected results are based on the survey data for 2004 of 32 counseling centers with 629 medicaments abused by 500 clients. The representativity was checked by comparison with the outpatient addiction statistics. The sample of counseling centers is representative for all addiction counseling centers in Germany. The dominant influence factor on the abuse of medicaments is the main diagnosis of the clients. Therefore, the analysis is separated for the main diagnoses as to alcohol, illegal drugs and medicaments. The statistical methods of confidence intervals and other statistical procedures are useful in proving data for cross-sectional and longitudinal analyses. In 2004 there was an increase of abused buprenorphine by 5.7% compared to the previous year. The rate of misuse of hypnotics, which is the largest group of abused medicaments, only slightly increased by 2.4%. The monitoring system PHAR-MON is a sensitive and valid monitoring system for the abuse of medicaments in addiction counseling centres. By documenting individual criteria of abuse in the new version of the documentation sheet, the results of medicament abuse can be analyzed in a more valid way. To improve the PHAR-MON system a study about reliability is planned. Because of the health risks associated with the abuse of medicaments, continuous information for physicians about the risks of medicament abuse is helpful to prevent negative consequences.