Mammary secretion from 32 primigravid heifers was obtained aseptically to determine frequency of bacterial isolation and incidence of intramammary infection near parturition. Quarter samples were collected 14 and 7 days prior to expected parturition, at parturition, and 7 and 14 days postparturition. Analysis of culture data indicated that 77.1% of samples were bacteriologically negative, and 15.7% contained coagulase negative staphylococci, 4.4% streptococci other than Streptococcus agalactiae, 3.8% coliforms, .8% coagulase positive staphylococci, and .1% Corynebacterium bovis. Frequency of bacterial isolation was highest in samples obtained prior to and at parturition. Thirty-five of 128 quarters were infected at parturition. Twenty-six of the 35 infections were caused by coagulase negative staphylococci, 4 by streptococci other than Streptococcus agalactiae, 4 by coliforms, and 1 by coagulase positive staphylococci. Twenty infections were observed during the early postpartum period. Coagulase negative staphylococcal infections decreased markedly. However, the number and type of primary pathogen infections during early lactation were similar to those at parturition.