A novel fluorimetric method has been developed for the determination of microgram quantities of bovine serum albumin (BSA) based on its enhancement effect of Nile Blue fluorescence at 670 nm, caused by binding of Nile Blue to BSA to produce a stable water soluble complex. The binding constant of micromole Nile Blue-BSA complex was estimated by Scatchard plot method. Under the optimal conditions, the increased fluorescence intensity was linearly related to BSA concentration in the range of 0.5-12.0 ㎍/mL. The detection limit was 0.2 ㎍/mL, and the relative standard deviation of six replicate measurements was 1.4% for 10.0 ㎍/mL BSA. There was little interference from amino acids, sugars and most of metal ions.