In the execution of their pharmacotherapy, many patients deviate from the prescribed treatment regimen. Reasons for noncompliance can be diverse and range from forgetfulness of the patient to attributes of the health care system. Besides increased health care costs, poor compliance causes both an endangerment to the patient and poor health outcomes. Therefore, it is crucial that compliance enhancement receives high priority. In the beginning of this process, noncompliance must be detected in daily practice. Moreover, various methods can provide valuable information about medication-taking behavior, time patterns, and reasons for noncompliance. Based on this assessment, appropriate measures to enhance compliance can be taken. In this article, the opportunities and limitations of compliance enhancement are discussed.