Objective：To investigate the effects of troglitazone on growth of thyroid papillary carcinoma cell line IHH-4 and the mechanisms possibly involved. Methods：Papillary thyroid carcinoma cell line IHH-4 was incubated with different concentrations of troglitazone and observed at different times, and the cell viabilities were measured through dimethylthiazol-diphenyltetrazolium bromide（MTT） assay. The cell cycles of the stimulated cells were analyzed by flow cytometer, and the expression of p27 mRNA was evaluated by semi-quantitative RT-PCR. Results：Troglitazone inhibited the proliferation of thyroid carcinoma cells in a dose-dependent and time-dependent manner（P < 0.05）. After treated by troglitazone，the proportion of cells in GO／G1 phase increased significantly（P < 0.05）, and p27 mRNA expression was up-regulated. Conclusion：Troglitazone inhibits the growth of papillary thyroid carcinoma cells by arresting the G1／S phase transition, so troglitazone could be a choice for the treatment of the aggressive thyroid carcinoma.