The cooking quality of 50 samples of Laird, Commercial Chilean and Eston lentils (Lens culinaris Medik.) grown at several locations in 1981 was determined with a Kramer press, and expressed as shear force in kilograms per gram. A shear force smaller than 4.0 kg/g was chosen to indicate cooked lentils, and one greater than 4.0 kg/g to indicate undercooked lentils. An optimum cooking time was established at which 50% or more of the samples had shear force values of 4.0 kg/g or smaller. Cultivar differences were evident in that the optimum cooking time for Commercial Chilean and Laird was 60 min, but only 30 min for Eston. Location had relatively less effect on cooking quality of the three lentil cultivars in 1981 as 95% of Laird, 88% of Commercial Chilean and 64% of Eston were cooked. These data were in contrast to a strong location effect observed in our previous study when only 55–58% of the lentils were cooked in the optimum time of 60 min. However, comparison of the 1980 and 1981 data showed a strong, seasonal effect on the cooking quality of lentils. Thus, the data showed that cooking quality in lentils was affected both by location and season. The cooked and undercooked lentils showed a contrasting microstructure. In undercooked lentils, unlike cooked lentils, the cells were intact and intercellular materials such as the cell wall and, presumably, middle lamella were visible. The microstructure of the lentils closely correlated with shear force values obtained with the Kramer press.Key words: Lentils, cooking quality, environmental effect, microstructure, scanning electron microscopy