DU90%--the number of drugs that account for 90% of DDDs--and adherence to guidelines in this segment were proposed by the Swedish Medical Quality Council (MKR) as indicators for assessing the quality of drug prescribing. We tested these indicators at a primary health care (PHC) center in Stockholm. Bar-coded prescriptions purchased at pharmacies were compared with the guidelines issued by the regional drug committee. The data were presented and discussed at the PHC center. Although the DU90% method neither examines the appropriateness of use nor provides outcome data, it was shown to be an inexpensive, flexible and simple method for assessing the general quality of drug prescribing.