The changes of Ca++ concentrations of endo- and perilymph were determined by using atomic absorption spectrophotometry in the guinea pig model which endolymphatic sac and duct were surgically obliterated one month ago. The results showed that the Ca++ concentrations of endolymph of hydropic ear was 0.181+0.129 mmol/L (n = 9), and that of the control group was 0.020+0.014 mmol/L (n = 10). The paired t test (P < 0.01) showed significant difference. In perilymph, the concentrations of Ca++ of hydropic ear was 0.679+0.340 mmol/L (n = 10), and that of the control ears was 0.730+0.385 mmol/L (n = 10). The paired t-test (P > 0.05) showed no significant difference. The principle of the increase of Ca++ concentrations in the endolymphatic hydrops was also discussed.