Abstract: This study was carried out at the Department of Plant Pathology of the Iranian Research Institute of Plant Protection during the period from January 2009 to December 2009 to develop some new bioformulations and evaluate their efficacy in promoting cotton seedlings growth characteristics. The interest in the use of biological approaches to replace chemical agents in fertilizing soils or improve plant resistance against phytopathogens is at present in continuous growth. In this regard, the use of Plant Growth Promoting Rhizobacteria (PGPR) has a potential role in developing sustainable systems for crop production. In search of efficient PGPR strains with multiple activities, we prepared eight bioformulations using two isolates of Pseudomonas fluorescens Q18 (B1) and CKK-3 (B2) which were isolated from rhizospheric soil and cotton roots in Varamin's cotton fields. Formulations included a talc-based powder and bentonite-based powder as inorganic carriers and peat and rice bran as organic carriers for increasing stability in interaction between associated PGPR and cotton plants. The results of a greenhouse experiment 60 days after sowing indicated that efficacy of BENT-B1, TAL-B1 and PT-B1 treatments were 1.38, 1.35 and 1.27 fold, BENT-B1, PT-B1 and TAL-B1 treatments were 1.42, 1.41 and 1.28 fold, RB-B2, TAL-B1 and RB-B1 treatments were 3.44, 3.37 and 2.90 fold and TAL-B1, RB-B2 and RB-B1 treatments were 2.60, 2.50 and 2.10, respectively on promoting seedling height, root length, seedling dry weight and root dry weight more effective than the control treatment.