Fifty-one specimens -- 18 from normal adults, 17 from oligospermic subjects, and 16 from azoospermic subjects -- were used for choline detection assay. The method is sensitive to three nanomoles(nm)/milliliter (ml). The choline content of semen was 16.69 micromoles(um)/ml, of male and female urine samples .041 and 0.019 um/ml, respectively, and of sputum samples 0.0100 um/ml. There was no significant difference in the choline content of normal, oligospermic, and azoospermic semen samples. Choline was not detected in vaginal fluid, male or female salivas and sera, or in mother's milk. Although choline was detected in some samples of dairy products, vegetable juices, and fruit juices whose stains are almost undistinguishable from human semen to the naked eye, its content in these specimens was much lower than in semen. Heated human semen specimens and seminal stains retained 70 percent of the pre-heating choline content. Similarly, storage of these samples at room temperature for 12 months allowed detection of about one-third to one-half of the original choline levels. Choline was even detected in aged seminal stains stored for 11 years. Intravaginal drugs did not significantly influence the detection of choline. The presence of semen in the vaginal content collected on mediocolegal autopsy could also be demonstrated by the detection of choline. The chemiluminescent assay for choline can be used for medicolegal determination of the presence of semen. 4 figures, 9 tables, and 29 references (Author abstract modified)