The aim of this study was to evaluate the long-term use of endometrial cytology with the Endopap sampler in clinical practice. Emphasis was placed on diagnostic accuracy, reduction of the number of curettages and cost per diagnostic test. Blind comparisons of two diagnostic tests were made during an observation period of five years. Endometrial cytology was compared with endometrial curettage as a standard if both samples had been taken within a six-month period and sufficient material had been obtained with both methods. A total of 468 women were studied. All had undergone endometrial curettage because of vaginal bleeding or impending hysterectomy. Abnormal endometrial cytology was found in 129 of 134 (96%) samples from patients with endometrial cancer, in 23 of 25 (92%) with invasive cervical cancer, in 30 of 31 (97%) with atypical endometrial hyperplasia and in 90 of 100 (90%) with endometrial hyperplasia but no atypia. Specificity was 84%. The annual numbers of fractional curettages decreased from 900 in 1986 to 298 in 1991. The study clearly showed that endometrial cytology is useful in clinical practice.