Human osteoblast-like cells SaOS-2 (ATCC HTB85) were seeded onto three kinds of hydroxyapatite (HA) ceramics sintered at different temperature (1200 degrees C, 1000 degrees C and 800 degrees C). Scanning electron microscopy (SEM) was conducted to detect the surface microstructure. Cells were cultured on these substrates for 6 and 12 days and cell proliferation rate and mRNA expression for osteocalcin, osteonectin, type I collagen and alkaline phosphatase and protein production for osteocalcin, bone sialoprotein and osteonectin were detected with quantitative in situ hybridization and immunocytochemistry techniques. SEM revealed that crystal particle size was affected by sintering temperature. Result showed that cell proliferation rate on HA ceramics sintered at 1200 degrees C was the highest. Osteonectin and type I collagen mRNA expression was not altered by sintering temperature. After 12 days in culture, bone sialoprotein, osteocalcin and osteonectin proteins levels were significantly (p<0.05) higher when SaOS-2 cells were cultured on HA sintered at 1200 degrees C, compared to the other two surfaces, suggesting that HA sintered at high temperature may be a better candidate for in vivo implantation. This result provides valuable information concerning the clinic application of HA ceramics sintered at different temperature.