Possibility of polyploidy induction by colchicine in “Balady” mandarins was investigated in vitro. Seeds were immersed in different concentrations of colchicine solutions (0.01%, 0.05%, 0.1% and 0.2%) for different durations (12, 24 and 48 hr), then cultured in vitro on MS medium at half strength. Seed survival percentage decreased by increasing colchicine concentration and duration of treatment showing the lowest percentage at 0.2% for 48 hr. The highest DNA content was recorded at 0.2% for 24 hr. Stomata No. per unit area was decreased by colchicine treatments; moreover stomata length and width were studied. The results indicated that colchicine treatment at 0.1% for 48 hr had the highest tetraploid induction efficiency percentage.