Plant height; stem thickness; fresh and dry weights of leaves and stems; numbers of leaves, trusses, flowers, and fruits; and leaf concentrations of Cl, Na, N-NO3, K, Ca, and Mg were measured in mature plants from 39 tomato accessions representing five species of Lycopersicon [L. esculentum Mill., L. peruvianum (L.) Mill., L. pimpinellifoliurn (Jusl.) Mill., L. hirsutum H. & B., L. pennellii (Corr.) D'Arcy] in response to various NaCl concentrations. Plants were irrigated with a nutrient solution, plus one of four levels of NaCl with electrical conductivities of 0.28, 0.63, 1.39, and 2.15 S·m-1. Characters were evaluated for each genotype taking into consideration: 1) the significant differences between NaCl concentrations, 2) the experimental errors in the analyses of variance, and 3) the uniformity of response to the salt concentrations. The characters that fulfilled these criteria for all 39 genotypes were: plant height, dry weights of leaves, fresh and dry weights of stems, and leaf concentrations of Cl and Na. However, other characters, although not generally applicable to the entire data set, were good indicators of response differences within a particular species. Leaf concentrations of N-NO3 and Mg were useful indicators in L. pimpinellifolium and L. esculentum and number of leaves and leaf concentration of Mg were useful indicators in L. hirsutum for responses of mature plants to salt stress.