OBJECTIVE--To determine the ability of a sensitive one step urine test to detect human chorionic gonadotrophin in women with suspected complications of early pregnancy. DESIGN--Test on women presenting to accident and emergency department with gynaecological problems over six months. Results were validated using a quantitative assay for human chorionic gonadotrophin in serum and urine. SETTING--Accident and emergency department and gynaecology wards of a university teaching hospital. SUBJECTS--130 unselected women. MAIN OUTCOME MEASURES--Detection of human chorionic gonadotrophin by one step test, presence of ectopic pregnancy, and results of quantitative analysis of chorionic gonadotrophin in serum and urine. RESULTS--79 women had a positive urine test result and 51 a negative result. All 12 women with ectopic pregnancy had a positive test result, although urinary concentration varied from 191 IU/l to 47,800 IU/l. Only one woman, who had a faintly positive result, was found not to be pregnant on subsequent examination. The sensitivity and negative predictive values of the urine test were 100% respectively. 33 women were sent home from the accident and emergency department with normal clinical findings after a negative urine test result. All these women had undetectable concentrations of chorionic gonadotrophin in matched samples of urine and serum. CONCLUSIONS--A simple, rapid one step test for chorionic gonadotrophin should be available for the initial evaluation of emergency gynaecological problems. The additional cost of the test is offset by not admitting those patients whose clinical findings are normal and who have a negative urine test result and by reducing the number of women requiring quantitative assays of chorionic gonadotrophin.