PIP: An analysis of in vitro research aimed at determining the effect of nonoxynol-9 against Chlamydia trachomatis concludes that clinical research is needed to resolve the issue. There are 3 reports that the spermicide killed Chlamydia. All used iodine stain, which detects glycogen, and fails to demonstrate immature organisms without inclusion bodies. The study that used a species specific fluorescent marker for Chlamydia membranes found no effect even with 50% spermicide. Another problem is cytotoxicity for the tissue culture cells used in the assay, which appears to be common even at low concentrations of nonoxynol-9. The timing of the inoculation of Chlamydia into the experimental cultures also appeared to affect the results differentially. It appears that controlled clinical trials will be needed to resolve this issue.