Orally administered, immediate-release (IR) drug products in the top 200 drug product lists from the United States (US), Great Britain (GB), Spain (ES), and Japan (JP) were provisionally classified based on the Biopharmaceutics Classification System (BCS). The provisional classification is based on the aqueous solubility of the drugs reported in readily available reference literature and a correlation of human intestinal membrane permeability for a set of 29 reference drugs with their calculated partition coefficients. Oral IR drug products constituted more that 50% of the top 200 drug products on all four lists, and ranged from 102 to 113 in number. Drugs with dose numbers less than or equal to unity are defined as high-solubility drugs. More than 50% of the oral IR drug products on each list were determined to be high-solubility drugs (55−59%). The provisional classification of permeability is based on correlations of the human intestinal permeabilities of 29 reference drugs with the calculated Log P or CLogP lipophilicity values for the uncharged chemical form.