Endometritis is the most frequent infectious complication of the puerperal period; with the objective to know the clinical characteristics, etiology and evolution of this disease we did a retrospective study of the endometritis cases among the patients of the Instituto Nacional de Perinatología (INPer) from January 1st, 1990 to May 31, 1991. During the revision period were diagnosed 120 cases, but we were able to examine only 90. In the 90% the resolution of the pregnancy was by means of caesarean. A 24.4% of the patients had premature rupture of the membranes. The 10% had diagnose of chorioamniotis. The latency period to develop postpartum endometritis was 120 +/- 66 hours, and post-caesarean 56 +/- 30 hours (p = 0.001). The symptom most frequent were fever (100), foul-smelling lochia (61.1%) and uterine tenderness (60%). The infection was polymicrobial, being the microorganisms most frequent isolated Staphylococcus coagulase negative, Escherichia coli and Peptostreptococcus. A 3.3% developed pelvi-peritonitis. One patient died.