A flow injection analysis (FIA) of sildenafil citrate (SLD) using UV detection is described in this study. The best solvent system was found to be consisting of 0.2 M phosphate buffer at pH 8 having 10% MeOH. A flow rate of 1 ml. min(-1) was pumped and active material was detected at 292 nm. The calibration equation was linear in the range of 1x10(-6)-5x10(-6) M. Limit of detection (LOD) and limit of quantitation (LOQ) were calculated to be 3x10(-7) and 8.9x10(-7) M with a R.S.D. 1.9 and 0.6% (n=7), respectively. The proposed method was applied to the determination of SLD in VIAGRA tablet, containing 50 mg active material. The results were compared with those obtained from UV-Spectrophotometry. The results showed that there is a good agreement between FIA method and the UV-Spectrophotometry. The validation studies were realised by the related applications and the results were evaluated statistically. According to the results, insignificant difference was observed between the methods.