In lentil (Lens culinaris Medik.) condensed tannins are responsible for seed coat darkening during storage and the associated reduction in crop quality. The vanillin-HCl method was used to measure tannin concentration. Tannins were present only in the seed coat. Tannin concentration in the seed coat of 87 lines from the USDA World Lentil Collection ranged from 35 to 93 g kg−1 and averaged 63.3 g kg−1. The zero-tannin trait of PI 345635 lentil was controlled by a single recessive gene (tan tan) that had pleiotropic effects on plant pigmentation and seed coat thickness. Heritability of tannin concentration among lines containing tannin was 66.4 ± 4.4%, based on the components of variance method. Selection for lower or higher tannin concentration in lentil should be effective.Key words: Lentil, tannin, tannin genetics, proanthocyanidin, Lens culinaris