In this paper, an ABA-deficient Pisum sativum mutant is physiologically characterized. A wilty pea line (wil) was backcrossed six times with a non-wilty line, and then selfed to obtain near-isogenic lines. These lines were used for further studies. The plants were grown hydroponically and at high relative humidity. The ABA-deficient mutant grew more slowly in mass and height and invested less dry matter in its roots. Mutant leaves wilted rapidly under drought conditions, and had a lower water content than wild-type leaves. ABA-deficient plants had fewer and smaller seeds than wild-type plants, but the weight ratio of reproductive to vegetative parts was similar in both lines. Seeds of mutant plants contained about five times less ABA than wild-type seeds. It is suggested that the lower growth rate of both vegetative and reproductive parts is not directly caused by the lower ABA content, but by disturbed water relations.