Search for neutrinoless double-. beta. decay of sup 100 Mo

We report the results of an experimental search for neutrinoless double-{beta} decay using isotopically enriched foils of {sup 100}Mo interleaved in a stack of 40 silicon detectors. With an exposure of 69.9 mole days, we place lower half-life limits on the {ital J}{sup {ital P}}=0{sup +}{r arrow}0{sup +} transition of 4{times}10{sup 21} yr (68% C.L.) and on the 0{sup +}{r arrow}2{sup +} transition of 4{times}10{sup 20} yr (68% C.L.).