Employing 7-15 resistant and 8-15 susceptible Japanese black pine (Pinus thunbergii Parl.) trees to pine gall midge (Thecodiplosis japonensis Uchida et Inouye) as samples, needle monoterpenes were analysed by GLC in January and June, and observation was made on the oviposition preference. Following results were obtained. 1. In January, the resistant trees showed higher contents of myrcene, limonene, β-phellandrene and terpinolene but lower contents of α-and β-pinene and camphene compared to the susceptible trees. But in June, α-pinene, camphene, limonene, β-phellandrene and terpinolene were higher and the content of β-pinene and myrcene were lower in the resistant trees than the susceptible trees. 2. The content of limonene was higher by the 6.8 percent and the content of β-pinene was lower by the 9.2 percent in the resistant trees than in the susceptible trees in June. 3. No preference for oviposition was found between resistant and susceptible trees. But in the resistant trees gall formation rate was quite lower than the susceptible trees. It was considered, therefore, that limonene and β-pinene content in the needle might be used as an indicator of the resistant Japanese black pine to the pine gall midge regardless of season.