The effects of beta sympathetic drugs on positive accommodation (accommodation for near vision) were studied in vervet monkeys. Isoproterenol, a beta sympathetic stimulator, depressed the positive accommodation function. It was not a complete antagonist since 3 to 4 diopters of accommodation remained. Only atropine, a parasympathetic blocker, could abolish these 3 to 4 D as well as the entire function. In many of the experimental animals, positive accommodation function was biphasic. The initial component had a flatter slope, lower amplitude, and lower threshold of stimulation than the second. The transition point of the components was between 2 and 4 D. Beta sympathetic stimulation appeared to abolish selectively the second component while parasympathetic inhibition abolished both components. It appeared that peripherally, parasympathetic inhibition was a more potent and thus more important mechanism in antagonizing positive accommodation than beta sympathetic stimulation.