Responding to the slogan of Health for All for the Year 2000, third world governments have expanded the provision of primary health services, and with it, the number of prescriptions has increased phenomenally. However, we know very little about how third world patients are using prescribed medicines. In order to assess the available information, we reviewed 37 empirical studies on compliance located through electronic lines and networking. By and large, the orientation of the studies is biomedical. The authors measure levels of compliance and advance recommendations to increase them. We found little consistency in the definition of compliance and a variety of methodologies used in its measurement. In spite of methodological problems, most researchers found low levels of adherence to medical regimens. Low levels of adherence raise questions about the quality of care, iatrogenic effects caused by the inadequate use of modern medicines, and the health and economic impact of health investments. At the same tie it is recognized that, given current prescribing practices and lack of efficacy of many medicines, compliance may add little to the quality of care. Compliance and prescribing behaviours should always be examined together and as part of quality of care assessments.