In this study, poly-beta-hydroxybutyrate (PHB) accumulation was investigated in 14 strains of Pseudomonas species. The bacteria were grown in nutrient broth medium at 30-37 degrees C for 48 h and the biomass was obtained by centrifugation. The cell wall of the cultures was lysed by ultrasonication and the PHB converted to crotonic acid by using sulfuric acid. The amount of crotonic acid was measured by UV spectrophotometer. The yield of PHB produced by the strains according to dry cell mass ranged between 2.16-67.37% (on dry cell mass). Pseudomonas cepacia G13, which produced the highest percentage yield of PHB was examined for PHB production over different incubation times (between 12 h and 84 h). Also, the yield of PHB production by this strain was determined in sugarbeet molasses (concentration: 1-6 g molasses/ 100 mL water) during appropriate periods (48 h). The highest yield of PHB production (70% on dry cell mass) was found at 3% molasses concentration.