By using the energy dispersive x-ray microanalysis technique the elemental composition of otoconia was analyzed in the normal fetal and normal adult, Shaker-1 and Shaker-2 mouse. There are no statistically significant differences in Ca concentration between otoconia seen in normal nineteenth gestational day (CBA/CBA) fetuses and that seen in 2-month-old animals. However, the standard deviation is almost three times larger in fetal than in adult otoconia. In all analyses, in both normal and mutant species, the following elements were identified: Na, Mg, P, S, Cl, K, and Ca. The present findings strongly indicate a calcite composition of otoconia in both normal and mutant species. Significant differences in Ca concentration (p < 0.05) occurred between the central and peripheral parts of large otoconia in normal mice. No difference in the elemental composition of otoconia in adult normal and Sh-2 mutants was detected. Differences occurred between adult normal and Sh-1 otoconia (Na — p < 0.05; Mg — p < 0.001; K — p < 0.001; Ca — p < 0.02). It is, however, unlikely that the shaking-waltzing behavior of Sh-1 and Sh-2 mutants derives from a minimal derangement of the elemental composition of otoconia.