We propose a basic skeletal feature representation of molecules with a graph colled NonTerminal vertex Graph W G ) that has no vertices of degree of 1. A sofhvare tool for NTG extraction was developed. and it was applied to structural feature analysis of dopamirie antagonists that interacf with four different ypes of receptors. The results suggest thaf the NTG analysis would be effective as an approach to chemical data mining and knonledge discovery 1011 structure-activip relations of the drugs.