To compare the efficacy and safety of a single daily instillation of nonpreserved timolol to a timolol maleate gel-forming solution in patients with chronic glaucoma or ocular hypertension already treated with latanoprost. A randomized, prospective, multicenter, open, parallel-group clinical trial was undertaken with 73 patients with chronic glaucoma treated with latanoprost and a timolol maleate gel-forming solution. In 36 patients, the previous regimen was substituted by nonpreserved timolol given instead of timolol maleate gel for 3 months. The changes in intraocular pressure (IOP) were recorded as well as local and systemic tolerance and patient compliance. At 3 months, both regimens were found equivalent in maintaining IOP control between D0 and D84. The difference with baseline was -0.08 +/- 2.22 mmHg and -0.38 +/- 2.41 mmHg in the nonpreserved timolol group and in the timolol maleate gel-forming solution group, respectively (CI 95% [-0.79; 1.38]). After 84 days of treatment, blurred vision (5.9%) and eyelid deposits (5.9%) were reduced in the preservative-free timolol group compared to the other group (respectively, 33.3% and 24.2%). These differences were statistically significant for both signs (blurred vision: p < 0.0001 and for eyelid deposits: p = 0.03). This short-term study has demonstrated the equivalence of nonpreserved timolol to timolol maleate gel-forming solution in terms of IOP control. Moreover, the local tolerance of nonpreserved timolol was better.