The mean latency and amplitude of P100 component of VEP were studied in forty three controls and eighty nine cases of thyroid dysfunction [Hypothyroid-28; Hyperthyroid-32 and probable Thyroiditis-29 (inclusive of 21 cytology proved)]. The mean latency in hypothyroid, hyperthyroid and probable thyroiditis subjects were 110.69, 111.41 and 109 m.sec in comparison to 101.91, 102.0 and 101.08 m. sec. respectively in controls (p < 0.005). The mean amplitude being 1.34, 6.34 and 2.41 microvolts in hypothyroid, hyperthyroid and probable thyroiditis subjects in comparison to 4.79, 4.16 and 4.59 microvolts respectively in controls (p < 0.005).