Over-the-counter vaginal lubricants have been shown to negatively affect in vitro sperm motility. The objective of this study was to estimate the effect of vaginal lubricant use during procreative intercourse on natural fertility. Women aged 30-44 years with no history of infertility who had been trying to conceive for less than 3 months completed a baseline questionnaire on vaginal lubricant use. Subsequently, women kept a diary to record menstrual bleeding, intercourse, and vaginal lubricant use and conducted standardized pregnancy testing for up to 6 months. Diary data were used to determine the fertile window and delineate lubricant use during the fertile window. A proportional hazards model was used to estimate fecundability ratios with any lubricant use in the fertile window considered as a time-varying exposure. Of the 296 participants, 75 (25%) stated in their baseline questionnaire that they use vaginal lubricants while attempting to conceive. Based on daily diary data, 57% of women never used a lubricant, 29% occasionally used a lubricant, and 14% used a lubricant frequently. Women who used lubricants during the fertile window had similar fecundability to those women who did not use lubricants (fecundability ratio 1.05, 95% confidence interval 0.59-1.85) after adjusting for age, partner race, and intercourse frequency in the fertile window. Lubricants are commonly used by couples during procreative intercourse. Lubricant use during procreative intercourse does not appear to reduce the probability of conceiving. II. © 2012 Lippincott Williams & Wilkins, Inc.