In this work, nano-size HA was produced from bovine bone. At various heat treatment temperatures, poorly crystalline, partially crystalline and crystalline forms of HA were obtained. PLA composites were prepared by incorporating various forms and contents of HA into PLA matrix. The characteristics of the obtained HA powders affected properties of PLA composites including mechanical properties, morphologies, PLA molecular weight,in vitrobioactivity andin vitrodegradation behaviors of the composites. In the case ofin vitrobioactivity study, all composites illustrated the induction of bone-like calcium phosphate compounds on their surfaces, especially the PLA/a-HA composites. [ABSTRACT FROM AUTHOR]