Aim and objectives: To evaluate the expression of beta–catenin in well differentiated and poorly / undifferentiated thyroid tumors. Also to identify tumors which may not have favourable outcome. Methods : In this study , paraffin blocks from 30 thyroidectomy specimens are stained with monoclonal antibodies reactive with beta–catenin. These include 22 cases of papillary carcinoma of thyroid (PTC) ( 16 cases of conventional PTC, 3 cases of Follicular variant, 2 cases of cribriform morular variant , 1 case of hobnail variant), 4 cases of Follicular carcinoma(FC), 3 cases of Medullary carcinoma (MC) and 1 case of Poorly differentiated carcinoma (PDC) Results : Papillary carcinoma conventional type, other variants of PTC and FC express residual membranous positivity and diffuse cytoplasmic positivity with occasional nuclear positivity. PTC,FVPC and hobnail variant show few nuclear inclusion positivity. PDC shows diffuse cytoplasmic positivity with severe loss of membrane positivity Conclusion: Loss of membrane positivity of beta catenin with cytoplasmic and nuclear expression correlates well with aggressive behaviour i.e increased invasiveness and metastasis.