Vascular reactivities to vasoactive substances were compared with ophthalmic and ciliary arteries (OAs and CAs) of Japanese monkeys. These two kind of arteries were perfused with Tyrode solution under a constant flow rate at 37 degrees C, respectively. Each drug solution was given by a microinjector into the endothelial side of the artery through a cannulated tubing, and responses were obtained as changes in perfusion pressure. Results were as follows: 1) Norepinephrine induced vasoconstriction in a dose-related manner in both arteries. The threshold dose was approximately 0.01 microgram in OAs and 0.1 microgram in CAs. The maximum value was approximately 45 mmHg in OAs and 20 mmHg in CAs. 2) Phenylephrine induced vasoconstriction in almost the same grade in both arteries. 3) Xylazine caused no significant change in perfusion pressure in both arteries. 4) Tyramine showed only small vasoconstrictor responses in both arteries. 5) 5-HT induced vasoconstriction in a dose-related manner in both arteries. The threshold dose was 0.001 microgram in CAs and 0.003 microgram in OAs, which indicated the smallest threshold dose in examined substances. However, the maximum increase in perfusion pressure was about 30 mmHg in OAs and 20 mmHg in CAs even at large doses. 6) PGF2 alpha induced a moderate increase in perfusion pressure, and the response in CAs was significantly greater than that in OAs. 7) KCl induced dose-dependent vasoconstriction. In CAs, the constriction induced by KCl was slightly greater than that in OAs but not significant.(ABSTRACT TRUNCATED AT 250 WORDS)