Abstract

Results are presented of the observation of atmospheric neutrino interactions in the Kamiokande detector in an exposure of 4.92 kt yr. The observed ratio of single ring μ-events to e-events (μe)data(μe)MC = 0.60+007−0.06 (stat.) ± 0.05 (syst.) suggests that the atmospheric vμ/ve ratio is smaller than expected. The implications of these results for neutrino oscillations are discussed.