In order to evaluate stem reserves and mobilization efficiency of bread wheat lines under drought stress at late growing season, an experiment was conducted on 16 advanced bread wheat lines (WS-87 series) using a randomized complete block design with 3 replications during 2009-2010 in Kabootarabad Agricultural Research Station, Isfahan. Drought stress was induced through irrigation cessation after heading. Length and weight of stem components including length and weight of peduncle, length and weight of penultimate internode and weight of remained internodes were measured in 5 steps at 10-day intervals from anthesis to physiological maturity. Mobilized dry matter and mobilization efficiency were calculated for each part of stem and their correlations with grain yield were estimated. Results showed that mobilized dry matter from peduncle varied from 13- 122 mg (lines 9 and 1, respectively), from penultimate internode varied from 75- 122 mg (lines 6 and 1, respectively) and from remained internodes varied from 51- 206 mg (lines 14 and 10, respectively). Total mobilized dry matter from stem varied from 186- 506 mg observed in lines no. 16 and 1, respectively. Mobilization efficiency for peduncle varied from 3.4- 26.8% (lines 9 and 3, respectively), for penultimate internode varied from 25.9- 48.6% (lines 6 and 8, respectively) and for remained internodes varied from 13.3- 42.8% (lines 14 and 10, respectively). Among three parts of stem, penultimate internode had the most important role in mobilized dry matter and mobilization efficiency. Grain yield positively correlated with peduncle length (r= 0.50^٭) and penultimate internode length (r= 0.53^٭).