AbstractExperimental and calculated data of drug lipophilicity, i.e. octanol/water partition coefficients (log Pobs) and hydrophobic fragmental constants (Σf, C log P) have been compared for the following four groups of drugs: antiarrhythmics (AA), β‐blockers (BB), phenothiazines (PT) and benzamides (BA).Measured log P values indicate significantly varying lipophilicity ranges in the case of these four groups (AA>BB>BA>PT).Comparison of the two calculative approaches with observed log P values yields almost identical qualities. Strongest discrepancies between calculative and experimental data are discussed on the basis of putative experimental pitfalls or in relation to structurally derived miscalculati