The purpose of this report is to present a few carefully checked observations as to the length of time sperm cells retain normal morphology and migratory power (not merely viability) in the reproductive tract of women, an important subject concerning which there is much vague speculation, many unsupported and widely varying opinions, and a paucity of convincing data. Vignes and Boros,1 as well as Belonoschkin,2 state that the survival of spermatozoa is not very long and probably does not exceed forty-eight hours, owing to the higher temperature of the pelvis as compared to that of the scrotum. The former, however, quote observations made by Huhner3 in which one case is included of sperm cells living as late as 102 hours after coitus. Macomber4 reported finding living sperm cells in the cervical secretions four days after copulation in seven cases, and as late as seven days after