The effect of methoxamine on retrograde flow of spermatozoa into the urinary bladder of domestic cats during electroejaculation and the incidence of retrograde flow during the collection of semen with an artificial vagina, or during mating was examined. In experiment 1, urine collected by cystocentesis prior to electroejaculation was azoospermic or contained few, nonmotile spermatozoa, whereas urine collected after electroejaculation contained more (P = 0.002) spermatozoa, and motile spermatozoa were evident in urine obtained from 6 of 8 cats. Administration of methoxamine hydrochloride (200 microgram/kg of body weight, IV) did not affect spermatozoal output or percentage of retrograde flow. Percentage of retrograde flow for control cats ranged from 61.18 to 92.95% (mean +/- SD, 80.00 +/- 14.28%) and for methoxamine-treated cats, ranged from 15.25 to 92.49% (mean +/- SD, 58.10 +/- 32.28%), but the difference was not significant. In experiment 2, an artificial vagina was used to collect semen from 5 of the 8 cats used in experiment 1. Urine collected by cystocentesis after ejaculation contained spermatozoa, and motile spermatozoa were evident in the urine from 4 of 5 cats. The mean (+/- SD) percentage of retrograde flow for these 5 cats was 46.82 +/- 31.67% (range, 14.56 to 90.32%). In experiment 3, each of the 5 cats that were used in experiments 1 and 2 were mated. Spermatozoa were recovered from the vagina of each mated female, and motile spermatozoa were also present in postejaculation urine obtained by cystocentesis from each of the 5 male cats. Mean total number of spermatozoa in the postmating urine was 29.42 +/- 33.58 X 10(6) (range, 0.22 X 10(6) to 76.05 X 10(6) spermatozoa). Anesthesia of cats with ketamine facilitated the obtention of urine by cystocentesis, but did not cause spermatozoal displacement into the urinary bladder. Results of this study confirm the fact that, in cats, appreciable numbers of spermatozoa are lost because of retrograde flow into the urinary bladder during electroejaculation. Recovery of spermatozoa from the urinary bladder after collection of semen with an artificial vagina or following natural mating, indicates that retrograde flow of spermatozoa is not an artifact derived from electrical stimulation but is a component of the ejaculatory process in cats.