Some new compounds, four kinds of 7-hydroxycoumarin and two kinds of 4-methyl-umbelliferon derivatives, were prepared. These and 13 kinds of esculetin and umbelliferon derivatives were used in testing anthelmintic action in vitro, using hog ascaris. Umbel-liferon derivatives gave lower melting points with increase of carbon atoms and in that order, increased anthelmintic action. Esculetin derivatives generally showed weak action while the introduction of a methyl radical in the 4-position of umbelliferon butyl ether resulted in the decrease of anthelmintic action.