Barley seeds (Hordeum distichon L.;cv. Pallas) were grown in a greehouse under four levels of biologically effective ultraviolet-A irradiation (effective daily doses 0, 7.92, 15.84 and 31.68 kJ m-2) for 127 days. Plants were measured and harvested at weekly intervals, beginning 15 days after germination, until reproductive maturity. Two different statistical models (Monomolecular and Michaelis-Menten) were used to analyze plant height. After several evaluation trials, the Monomolecular model {W = A [1 -exp (-Kt)]} was selected as being the best for comparisons of W (height) vs t (time after sowing) at any u.v.-exposure. Through the use of this statistical model, comparative analyses were performed among the different exposure groups. When plants were exposed to the highest u.v.-A dose (31.68 kJ m-2) a significant growth decrement was detected 6 weeks after sowing. At intermediate u.v.-A exposures (7.92 and 15.84 kJ m-2) no deleterious effects on plant height were observed at the end of the experiment. © 1988.