Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by many bacteria as carbon and energy reserves, these polymers have similar characteristics than petrochemical derived plastics. In consequense, PHAs can to substitute the synthetic plastics. To insolate PHA-producing – bacteria, several soil samples were collected of different zones of Departament of Nariño, Colombia, The qualitative selection of the strains with capacity of synthesis of the biopolymer was evaluated by the technique of the Red Nile. A bacterial strain of Bacillus mycoides presented the highest values in productivity (300 mg/l) and yield (Yp/s 0.2). The GC analysis of the simple of the plastic produced by this strain established that the PHA corresponds to the copolymer Poly (HB – co – HV).