Small hand-held microscopes have been developed for self-observation of salivary ferning patterns to detect the fertile time of a woman's menstrual cycle. The purpose of this study was to evaluate one such microscope, the Lady Free Biotester, by comparing it with the self-observation of cervical-vaginal mucus and with the self-detection of luteinizing hormone (LH) in the urine. Twelve natural family planning teachers (average age 34.6 years) observed their cervical-vaginal mucus, tested their urine for LH, and observed salivary and cervical-vaginal mucus ferning patterns (with the Lady Free Biotester) for two menstrual cycles. Data indicated that there was a strong correlation between the LH in the urine and the peak in self-observed cervical-vaginal mucus ferning (r = 0.99, p < or = 0.001) and salivary ferning (r = 0.98, p