Plant senescence is important process for plant development, and is genetically regulated in the last stage of organ development. Senescence is one type of programmed cell death(PCD) that occurs in plants. Previously, several senescence-associated genes(SAGs) of cucumber(Cucumis sativus L.) were selected to study the gene expression patterns and to characterize the water-stress response which may affect in those genes expression. The genes are Sen 36(FHA domain proteins encoding gene), Sen 49(『-carotenoid and 』-carotenoid synthesis related), Sen 54(metallothionine encoding gene), Sen 80(unknown gene), Sen 124(DEAD Box RNA Helicase encoding gene) and Sen 140(HUA Enhancer 2 encoding gene). First, natural senescence was examined from the days at 14th, 21th, 28th and senescence stage Ⅰ(50% yellow; SI), senescence stage Ⅱ(70% yellow; SⅡ) and senescence stage Ⅲ(>90% yellow; SⅢ) according to chlorophyll contents in cucumber cotyledons. Secondly, water-stress was applied to the cotyledons at day 14 after seed sowing. The cotyledons were used for total RNA purification and then cDNAs were synthesized. The genes expression level was examined by PCR experiment. In natural senescence, Sen 36 showed strong gene expression at the stage of senescence development in cucumber cotyledon. Sen 49 and Sen 54 were consistently expressed in all developmental stages. Sen 80 gene showed some fluctuation in gene expression, but the gene is active throughout development. Sen 124 and Sen 140 genes were expressed in all stages of development. In water stress experiment, Sen 36 gene showed inconsistent expression. And rest of the genes(Sen49, Sen54, Sen80, Sen124 and Sen140) were similar to that of the natural senescence results which expressed consistently.