The propensity for anxiety-related behavior has been studied by comparing two highly inbred strains of mice, ABP/Le and C57BL/6ByJ, in two behavioral procedures, open-field and light-dark preference. Their Mendelian F2 population allowed us to evaluate the putative involvement of four easily identifiable loci in anxiogenic processes. In fact, chromosomal regions containing the brown, pink-eyed dilution and short-ear loci on the 4th, 7th and 9th chromosomes respectively are associated with anxiety-related behavior patterns. In addition, binding of [3H]flumazenil to brain GABA(A) receptors was measured as a biochemical index that may be associated with observed behavior patterns.