Nine hundred and seventy-six Icelandic schoolchildren (489 male and 487 female) were surveyed for occurrence of torus mandibularis. No sexual dimorphism was observed but there was a statistically significant difference between areas. A highly significant positive association between age and frequency of occurrence and size was also observed. Single tori were more prevalent than multiple ones and also appeared earlier. Symmetrical occurrence predominated, but when unilateral, tori were more often found on the right side. Secular changes in the incidence of torus mandibularis among Icelanders suggest the strong influence of environmental factors.