Most women have symptoms of premenstrual dysphoric disorder (PDD) and 3-10% have symptoms that interfere with either work or social life. The diagnosis of PDD is based on recurrent and persistent symptoms which are confirmed in repeated evaluations. The epidemiology has not been established because of difficulties in studying this disorder. The 1-year prevalence of PDD symptoms of an intensity and frequency to meet DSM-III-R criteria in a group of women representative of the general population of Burgos (Spain) was studied using a PDD scale based on DSM-III-R criteria. On average, each symptom occurred in 28.6% of women in many or every cycle during the study year. 30.5% of women scored over 20 on the scale, meaning that they had at least 5-10 of the DSM-III-R criteria in every menstrual cycle. Symptom intensity was significantly greater in women whose work or social life was affected, who consulted for PDD, were treated for PDD, and had less-skilled jobs. The scale had a high internal consistency (alpha-0.84). Factorial analysis detected "dysphoria" as the main symptom, the physical symptom "edema", a secondary "psycho-social" factor, and "pain". Discriminant analysis of the ten items on the scale as a function of the cutoff score of 20 correctly identified 94% of the women meeting DSM-III-R criteria.