In a retrospective survey of a large obstetrical ultrasound experience, 10 echogenic adnexal masses in nine patients with a coexistent intrauterine pregnancy were detected and analyzed. Definitive follow-up data available for seven of the nine patients disclosed three ovarian teratomas, two hemorrhagic corpus luteum cysts, one endometrioma, one inflammatory mass, and one colonic pseudomass. In one additional patient, an echogenic ectopic pregnancy with an intrauterine pseudogestational sac simulated the above entities. Conservative management with follow-up sonography is generally indicated for echogenic masses coexistent with first-trimester intrauterine pregnancies.