In order to evaluate the effects of various lengths of cutting and different concentrations of indole butyric acid (IBA) on Bougainvillea spectabilis rooting, a research in outdoor conditions was conducted in Khorramshahr between march 2010 and may 2011. A factorial experiment was performed in a randomized complete blocks design with four different lengths of hardwood cuttings (5, 10, 15 and 20 cm) and seven IBA levels (0, 500, 1000, 1500, 2000, 2500 and 3000 mg/l) in 4 replicates (each replicate contained 10 cuttings). The Measured factors included rooting percent, root number, root length, fresh and dry weight of roots. SPSS software for statistical analysis and comparison of means was performed by Duncan's test at 5% level. The results showed that the highest rooting percentage belonged to 2000 mg/l of IBA, which led to increasing root length, root number, root fresh and dry weight at 5% level. Results also indicated that the highest rooting percent of cuttings, root fresh and dry weight and root number was obtained with 15 cm cutting. Therefore, the highest rooting percentage belonged to 2000 mg/l of IBA and 15 cm cutting.