Seventy-seven patients with ectopic pregnancy underwent culdocentesis; the tap was positive in 70%, negative in 10% and inadequate in 20%. A positive tap was significantly associated with a low hematocrit but was often obtained in patients without hypotension, tachycardia, peritoneal irritation or tubal rupture. While patients with peritoneal irritation were significantly more likely to have a large hemoperitoneum, many with 500 ml or more of hemoperitoneum did not have peritoneal irritation, hypotension, tachycardia, low hematocrit or tubal rupture. Culdocentesis is valuable for evaluating the patient suspected of having an ectopic pregnancy, and the absence of tachycardia, hypotension, low hematocrit or peritoneal irritation should not dissuade one from performing the test. A positive tap does not indicate tubal rupture, and a large hemoperitoneum may accumulate in its absence.