Germination of tomato (Lycopersicon esculentum Mill.) seeds in petri dishes at various levels of water stress was comparable, except under conditions of severe stress when a PEG pretreatment improved final percentage germination and enhanced the onset and rate of germination. At intermediate or high watering levels, PEG-pretreated seeds germinated more rapidly than untreated seeds, but final germination was not altered by PEG. Germination of seeds in soil, under controlled laboratory conditions, was similar to that in petri dishes except under the driest conditions (5% ASM) when little emergence occurred whether the seeds were pretreated or not. A majority of the seeds which failed to germinate after 2 weeks under dry soil conditions were still viable, since subsequently they could be induced to germinate by moistening the soil to 100% ASM. Water requirement of tomato seeds for optimal rate of germination was cultivar dependent; PI-341988 seeds germinated well at 60% ASM or greater, whereas ST-24 required 100% ASM for best germination.