Solid free-form fabrication (SFF) technology is used to fabricate scaffolds with controllable characteristics including well-defined pore size and porosity. The multi-head deposition system (MHDS), one form of SFF technology, may be more advantageous than others for fabricating scaffolds because a MHDS does not require the use of a cytotoxic solvent. This method, however, may induce the thermal degradation of raw materials and a subsequent decrease in the material's molecular weight, whereby hydrolytic degradation, resulting in acidic by-products, might be accelerated. This study investigated whether fabrication of poly(lactic-co-glycolic acid) (PLGA) scaffolds using a MHDS with various residence times in the heating step induces thermal degradation and affects the proliferation of cells seeded on the scaffold in vitro. To answer this question, we fabricated porous three-dimensional PLGA scaffolds using residence times of 1, 3, 5 and 7 days for groups 1 through 4, respectively. Degradation behavior of the scaffolds was observed for 7 weeks in phosphate-buffered saline solution (pH 7.4) at 37 degrees C. The molecular weight, glass transition temperature and mechanical properties were compared for PLGA scaffolds fabricated with each of the four residence times at 120 degrees C. The proliferation rate of MC3T3-E1 cells grown on each group of scaffolds was compared to investigate the effect of acidic by-products on the growth of seeded cells in vitro. The heat process applied in fabrication of SFF-based PLGA scaffolds induced considerable thermal degradation followed by a decrease in molecular weight and mechanical compressive strength of the scaffolds in groups 3 and 4, which had more than 3 days residence time. Moreover, the cell proliferation rate was significantly higher for group 1 than for groups 3 and 4.