PIP: Laboratory tests designed to measure the spermicidal effectiveness of contraceptive jellies and creams after dilution and mixing were carried out. 87 materials were tested. The number of minutes during which motion of the sperm continued in a column of human semen 2 mm in diameter and 5 mm long in contact with a contraceptive material was computed. The average spermicidal activity of the 51 jellies tested was higher than for the 16 suppositories and still greater than for the 20 creams. The immobilization times were measured of rice flour jellies containing sodium chloride in concentrations of 10%, 20%, and 30% of the water present. The 30% sodium chloride jelly showed the shortest immobilization time of any of the preparations, 41 minutes, whereas the time of the 10% mixture, 12 minutes, was shorter than that of 90% of the commercial preparations tested in 1951 and of 80% of those tested in 1953 (the present study). Based on the 87 commercial contraceptive mate rials reviewed, the data indicate a maximum diffusion spermicidal time of 195 minutes for desirable materials.