Various biological activities (enzyme inhibitory potency, lipoxygenase inhibition, tadpole narcosis, vapor toxicity and heat of vaporization) of molecules are correlated with molecular descriptors. The molecular descriptors used in this works are molecular connectivity index, Wiener distance index and ad hoc descriptor, which can encode information about branching, size, cyclization, unsaturation, hetero atom content and polarizability. It is found that calculated values from multiple regression equations are in a good agreement with experimental data on five biological activities of alcohol, ester and ketone compounds.