The correlation between plasma protein binding, the volume of distribution, molecular weight, and percentage removed by hemodialysis was investigated in 89 drugs using information available in the literature. The correlation was significantly linear between dialyzability and plasma protein binding, as well as with the reciprocal volume of distribution. This is in agreement with the theoretical deduction of dialyzability from diffusion and convection kinetics. Multiple linear regression analysis revealed that only 27% of the variance in dialyzability could be explained by plasma protein binding (17%), the volume of distribution (6%), and the molecular weight (4%) of the drugs. Therefore, the dialyzability of drugs can not be predicted reliably.