Fifteen patients with symmetrically increased intraocular pressure (IOP) participated in a single-masked random 30-day clinical trial comparing 4% pilocarpine hydrochloride gel applied at bedtime to one eye with 4% pilocarpine hydrochloride drops instilled four times daily in the fellow eye. Both forms of pilocarpine reduced IOP significantly at 8 A.M., 12 noon, and 4 P.M. (P < .01). At these times there was no significant difference in effect between the two forms of pilocarpine (P > .05). The mean IOP of eyes treated with gel showed no significant difference from the pretreatment value at 10 P.M. (P = .37), whereas at this time eyes treated with drops did maintain a significant IOP reduction (P = .02). At 10 P.M. pilocarpine drops reduced IOP significantly more than did pilocarpine gel (P = .002). Pupil diameter was affected by the gel and drops in a similar pattern to that of IOP. Patients tolerated the gel with few side effects and were pleased by the convenience of administration once daily.