A commercially available, disposable blade in a spring-loaded cassette was used to measure oral mucosa bleeding times (OMBT) of ketamine/acepromazine-anesthetized cats. The OMBT were determined in cats homozygous for Chediak-Higashi syndrome (CHS; n = 7), cats heterozygous for CHS (n = 6), and cats homozygous for Hageman factor (factor XII) deficiency (n = 5). In addition, OMBT were determined in three groups of normal cats: random-source cats (n = 14), inbred normal relatives of the cats with CHS (n = 7), and inbred normal relatives of Hageman factor deficient cats (n = 9). No significant differences were found in the OMBT of the three groups of normal cats. The mean OMBT for all 30 normal cats was 1.9 minutes ± 0.5 minutes s.d. Compared to the normal cats, those homozygous for CHS had significantly prolonged OMBT (14.1 ± 3.3 minutes; ±p >0.05). The mean OMBT of cats heterozygous for CHS (2.6 ± 0.8 minutes) was also significantly longer than the OMBT of the combined normal group. The mean OMBT of the CHS heterozygotes, however, was not significantly longer than that of their normal relatives (OMBT = 1.8 ± 0.5 minutes), probably because of the low number of cats in this subgroup of normals. As expected, the OMBT of cats homozygous for Hageman factor deficiency (2.3 ± 0.3 minutes) were not significantly prolonged.