Summary. Twenty-nine ejaculates of semen were collected from five stallions (four thoroughbreds and one quarterhorse) for this study. The volume of semen, cell count and gel volume/ejaculate averaged 105 ml, 143 × 106/ml and 36·8 ml, respectively. Dry matter content of semen was 3·00%, gel 2·84% and seminal plasma 2·77%; while micrograms of dry matter/106 cells averaged 19·8. The lipids from spermatozoa, seminal plasma and gel from each ejaculate were extracted, and the pooled lipid samples of each fraction were analysed quantitatively for the major lipid classes. Spermatozoa contained 14% lipid, while the seminal plasma and gel contained 2·07% and 2·10%, respectively. The spermatozoal lipid contained phospholipid (58·7%), cholesterol (13·7%), diglycerides (9·0%), triglycerides (8·0%), and wax esters (10·6%). The seminal plasma and gel contained the same lipid classes and the percentages of each were in the same order as above, for seminal plasma: 74·4, 12·1, 3·6, 3·2 and 6·7; for gel: 75·0, 10·0, 5·3, 4·3 and 5·4.