Rat skin permeation of various nonsteroidal antiinflammatory drugs (NSAIDs) was investigated in vitro using Franz diffusion cell at $37^{circ}C$. The effect of various skin permeation enhancers was also observed as a preliminary study of developing transdermal delivery systems of NSAIDs. Lipophilicity of NSAIDs was determined from thε partition coefficient (log P) in 1-octanol/water and 1-octanol/IPB mutual-saturated solutions. The solubility was determined in water, isotonic phosphate buffer (IPB), and propylene glycol (PG) at $37^{circ}C$. The rat skin permeation rate of acetaminophen, piroxicam, and aceclofenac was almost negligible, although they were saturated in PG. Addition of 1 % permeation enhancer increased the permeation rate of ketoprofen, ketorolac, and diclofenac. However, the skin permeation rate of ibuprofen did not increase with the addition of various enhancers. Among the permeation enhancers testεd, oleic acid was the most effective for various NSAIDs. Based on the daily dose, lipophilicity, and the skin permeation ratε achieved in this study, ketoprofen and ketorolac seem to be the most promising drug candidates for transdermal delivery systems, especially when formulated with unsaturated fatty acids, such as oleic acid.