Hypocotyl explants of three cultivars of melon (Cucumis melo. L.) (cvs. Revigal,. Topmark and Kirkagac), and a cucumber (C. sativus L. cv. Thoz) rapidly directly regenerated multiple shoots on Murashige and Skoog medium augmented with 4.4 mum benzyladenine. Regeneration from the hypocotyl resulted in nearly 100% diploid shoots, whereas, regeneration from the cotyledons resulted in 40% to 70% polyploid regenerants. Regeneration from cotyledon explants of melon cv. Revigal required light, whereas regeneration from hypocotyl explants of melon cv. Revigal occurred in both light and darkness. Direct regeneration also occurred from the hypocotyl of cucumber cv. Thoz in both light and darkness, even though cotyledonary explants did not regenerate buds or shoots under the same conditions. This is the first report of regeneration from the Cucumis genus producing a fully diploid plant population.