Premenstrual syndrome (PMS) is a disruptive set of emotional and physical symptoms that regularly occur in the one to two weeks before the start of each menstrual period. Symptoms resolve around the time menstrual bleeding begins. Symptoms vary, though commonly include one or more physical, emotional, or behavioral symptoms, that resolve with menses. The range of symptoms is wide, and most commonly are breast tenderness, bloating, headache, mood swings, depression, anxiety, anger, and irritability. To be diagnosed as PMS, rather than a normal discomfort of the menstrual cycle, these symptoms must interfere with daily living, during two menstrual cycles of prospective recording. PMS-related symptoms are often present for about six days. An individual's pattern of symptoms may change over time. PMS does not produce symptoms during pregnancy or following menopause.

Diagnosis requires a consistent pattern of emotional and physical symptoms occurring after ovulation and before menstruation to a degree that interferes with normal life. Emotional symptoms must not be present during the initial part of the menstrual cycle. A daily list of symptoms over a few months may help in diagnosis. Other disorders that cause similar symptoms need to be excluded before a diagnosis is made.

The cause of PMS is unknown, but the underlying mechanism is believed to involve changes in hormone levels during the course of the whole menstrual cycle. Reducing salt, alcohol, caffeine, and stress, along with increasing exercise is typically all that is recommended for the management of mild symptoms. Calcium and vitamin D supplementation may be useful in some. Anti-inflammatory drugs such as ibuprofen or naproxen may help with physical symptoms. In those with more significant symptoms, birth control pills or the diuretic spironolactone may be useful.

Over 90% of women report having some premenstrual symptoms, such as bloating, headaches, and moodiness. Premenstrual symptoms generally do not cause substantial disruption, and only qualify as PMS in approximately 20% of pre-menopausal women. Antidepressants of the selective serotonin reuptake inhibitors (SSRI) class may be used to treat the emotional symptoms of PMS.

Premenstrual dysphoric disorder (PMDD) is a more severe condition that has greater psychological symptoms. PMDD affects about 3% of women of child-bearing age.

Any disruptive, cyclical symptom could be a symptom of PMS, and some sources have suggested that the number of claimed symptoms could exceed even 200. However, some symptoms are relatively common in PMS. Common emotional and non-specific symptoms include stress, anxiety, difficulty with sleep, headache, feeling tired, mood swings, increased emotional sensitivity, and changes in interest in sex. Problems with concentration and memory may occur. There may also be depression or anxiety.

Common physical symptoms include bloating, bilateral breast tenderness, and headache.

The exact symptoms and their intensity vary significantly from person to person, and even somewhat from cycle to cycle and over time. Most people with premenstrual syndrome experience only a few of the possible symptoms, in a relatively predictable pattern. Additionally, which symptoms are accepted as evidence of PMS varies by culture. For example, women in China report feeling cold but do not report negative affect as part of PMS, while women in the US report negative affect but not feeling cold as part of PMS.