Niosomes (non-ionic, surfactant-based vesicles) containing rifampicin of 8-15 mu m in diameter were prepared using Span-85 and cholesterol in various molar fractions. The process variables that could affect the physical characteristics of niosomes and in vitro release of the drug from the niosomes were studied and optimized. In vivo distribution studies of the prepared niosomes found that 65% of the drug could be localized in the lungs by controlling the niosome size.