A study was conducted to evaluate the effects of Plant Growth Promoting Rhizobacteria (PGPR) inoculants including four strains of Azotobacter chroococcum, Azospirillum lipoferum, A. brasilense and Pseudomonas fluorescence on dry matter accumulation of late maturing Maize(Zea mays L.) hybrids, SC704, SC700 and a promising single cross B73×K18. A factorial experiment was conducted in research field of Seed and Plant Improvement Institute (SPII) of Karaj in 2004 and 2005. In this study, hybrids seeds were inoculated by various PGPRs. At physiological maturity, plant and stem, leaves, tassel, ear, husks, cob and grain dry matter and harvest index were determined. Results revealed that, except tassel and husks dry matter, other traits affected by year, hybrid and PGPR. SC704 and SC700 which inoculated by all bacteria exhibited the highest plant, stem, leaves, cob and ear, dry matter and harvest index in the second year. Also in two years, three hybrid seeds inoculated by all bacteria had the most effect on dry matter partitioning. This treatment caused 48, 15, 4 and 30% increase in whole plant, leaves, stem and grain dry matter, respectively. Moreover, 34% increase in harvest index was detected. The results indicated that studied hybrids dry matter partitioning pattern affected by PGPR. Also application of PGPR changed plant organs dry matter partitioning trend to sources and sinks. Also the rate of this increase for leaves as main photosyntetically organs and ear was higher resulting in higher harvest index.