We have investigated the promotive effect of various agents on percutaneous absorption of 6-carboxyfluorescein (CF), a water-soluble fluorescent dye, as poorly absorbable drugs. The absorption of CF was determined by measuring rat plasma CF levels. As an absorption promoter, several reagents such as surface-active agents, protein solubilizers and permeation promoters were used. The used concentration of the reagents was determined so as not to make a trauma on the skin. As results, plasma CF levels following the co-administration of 0.05 w/v% sodium dodecyl sulfate and 0.1 v/v% 2-mercaptoethanol showed the highest values. Plasma CF level was increased 40 times as compared to that of control experiment and was increased 9 times as compared to that of pretreatment with 4 w/v% calcium thioglycolate which was reported previously as a strong absorption promoter for theophylline by us. When the stratum corneum, having a barrier function for percutaneous absorption of many compounds, was removed mechanically, plasma CF levels of control experiment and pretreatment with 4 w/v% calcium thioglycolate were increased remarkably. However, plasma CF level after the co-administration of 0.05 w/v% sodium dodecyl sulfate and 0.1 v/v% 2-mercaptoethanol did not show a considerable difference as compared to that of the case with the presence of the stratum corneum.