A retrospective study of patients found to have ectopic pregnancy was undertaken to determine the relative usefulness of culdocentesis and ultrasound in the evaluation of early and late presentations. The patient's history was used as the sole determinant of gestational age, and results of culdocentesis and/or ultrasound were reviewed. In early presentations (less than 42 days gestation), 38% of ultrasound examinations and 89% of culdocenteses performed were positive. In late presentations, 93% of ultrasound examinations and 70% of culdocenteses performed were positive. The difference between the modalities' performance was significant (P less than .05) for both early and late presentations. These data could provide the basis for a prospective study to test the hypothesis that culdocentesis is the diagnostic test of choice in early suspected ectopic pregnancy, whereas ultrasound is more likely to yield clinically useful information in patients presenting after six weeks gestation.