OBJECTIVE: This study examines mean days between patients refilling their glaucoma prescriptions for latanoprost, travoprost, and bimatoprost. METHODS: Patients with an initial NDC pharmacy claim for the 2.5 mL bottle of latanoprost, travoprost, or bimatoprost between September, 2002 and December, 2002 were identified from a retail pharmacy database. Continuous eligibility was defined by at least one claim for the same lipid agent and bottle size one year later between October, 2003 and December, 2003. The mean number of days between claims, mean number of refills, the average cost per patient per year and the annual refill cost differences between cohorts were calculated. Due to limitations inherent in claims data analyses, efficacy data were not part of the analysis. RESULTS: The mean number of days between refills for latanoprost was 47, for travoprost 53, and for bimatoprost 52. The among-group difference was statistically significant (p<0.0001). The mean number of refills per year was calculated to be 7.8, 6.9, and 7.0 for latanoprost, travoprost, and bimatoprost, respectively. Based on the mean number of refills, the average cost per patient per year was $429.11 for travoprost, $434.70 for bimatoprost, and $455.36 for latanoprost. The incremental refill cost savings per year for the latanoprost population (n=79,820) would be approximately $2 million by using bimatoprost or travoprost instead of latanoprost. CONCLUSIONS: Both bimatoprost and travoprost have higher average days between refills, suggesting these two products may last longer than latanoprost. Consequently, an additional refill cost savings is realized by using bimatoprost or travoprost over latanoprost.