Number 86 (Story #2), June 26, 1992 by Phillip F. Schewe and Ben Stein THE SUDBURY NEUTRINO LABORATORY in northern Canada, to be commissioned in early 1995, will be the first facility that can detect muon and tau neutrinos as well as the electron neutrinos measured recently by the Gallex detector in Italy. Although Gallex detected fully two-thirds of the solar electron neutrinos predicted by theory, it nonetheless leaves open the possibility that electron neutrinos may be converted to other types of neutrinos on their way to earth via the proposed Mikheyev-Smirnov-Wolfenstein (MSW) mechanism. One of the first objectives of the Sudbury experiment will be to look for evidence of the MSW mechanism at work. Another next-generation neutrino detector is Super-Kamiokande, to be finished in Japan in 1996. (Science, 12 June 1992.)