AIMS: To investigate the subretinal fluid (SRF) penetration of ciprofloxacin following topical, oral, and combined administration. METHODS: 34 patients undergoing conventional retinal reattachment surgery were randomly assigned to three groups. Twelve patients received topical ciprofloxacin, 11 patients received oral ciprofloxacin, and the other 11 patients received combined drug administration. SRF drug level was measured by using high performance liquid chromatography method. RESULTS: The highest drug concentrations of all tested modes were attained following combined administration and lowest following topical administration (p<0.001). The SRF drug concentration following oral administration was also significantly higher than that of topical administration (p<0.001). Concentrations after oral and combined administration did not differ significantly (p = 0.217). CONCLUSIONS: Topical ciprofloxacin can penetrate SRF. Ocular bioavailability of ciprofloxacin in SRF after oral and combined administration is equivalent.