The thermoluminescence (TL) properties of plagioclase separates from 10 independently dated alkalic basalts from the Hawaiian Islands were studied for the purpose of developing a TL dating method for young volcanic rocks. The samples range in composition from alkalic olivine basalt to trachyte and in age from 4500 years to 3.3 m.y. The TL process in basaltic plagioclase appears to involve the production of structural defects by radioactive decay particles, as well as filling of traps associated with these defects with excited electrons. The ratios of natural to artifical TL for the samples up to 200,000 years old increase at a uniform exponential rate; the ratios for samples greater than 1 m.y. old appear to be attenuated, probably due to saturation effects. The equation for the best fit line through a plot of the TL ratios versus known age for the younger samples constitutes a TL age equation suitable for assigning TL ages to other samples of similar origin and chemical composition. The probable age range of the method is about 2500 to at least 250,000 years. The precision of the ages is approximately ¿5% for samples older than 50,000 years; concordance with K-Ar ages is tentatively estimated to be approximately ¿10%.