Because of the prevalence, chronicity and distress caused by premenstrual symptoms (PMS), diagnosis and effective treatments are important information for clinicians. The DSM-IV requires at least five specified symptoms for premenstrual dysphoric disorder (PMDD), a severe dysphoric form of PMS, while the ICD-10 requires only one distressing symptom for a diagnosis of PMS. Many women who seek treatment fall between these two diagnostic approaches, and standard diagnostic criteria for clinically significant PMS are needed. A diagnosis of PMS consists of determining the timing of the symptoms in relation to menses, meaningful change between post- and premenstrual symptom severity and a clinically significant severity of the symptoms. A differential diagnosis to distinguish PMS from other medical and psychiatric conditions is important for appropriate treatment. No hormone or laboratory test indicates a PMS diagnosis. The current diagnostic standard requires confirmation of subjective symptom reports by prospective daily diaries. Diagnostic criteria for PMS must recognize the broad range of symptoms, the temporal pattern of the symptoms and the critical issue of symptom severity, which differentiates clinically significant PMS from normal menstrual cycle changes.