A biodegradable composite with silicon-species releasability was prepared using poly(l-lactic acid) (PLLA) and silicon-doped vaterite (SiV) particles. SiV with particle diameters of approximately 1 mum was prepared using aminopropyltriethoxysilane (APTES) as the silicon species by a carbonation process and then mixed with PLLA in methylene chloride according to a SiV to PLLA weight ratio of 1:2, resulting in the preparation of composite slurry. A composite film was prepared by dipping a cover glass in the slurry. The composite films were incubated in a culture medium for 7 days and the silicon concentration of the medium was measured to estimate the species releasability of the composites. A trace amount of silicon species was continuously released from the composites for 7 days, the amount depending on the content of APTES in SiV. On the composite releasing silicon species, mouse osteoblast-like cells (MC3T3-E1 cells) were significantly stimulated to proliferate and differentiate in comparison with those on a composite containing no silicon species. The proliferation of the cells on the composites releasing larger amounts of silicon species (0.51mgl(-1)day(-1)) was higher than that on the composites releasing smaller amount of the species (0.21mgl(-1)day(-1)). The silicon species in the composites were effective in enhancing the cellular functions. The composites were expected to be useful as a scaffold material for bone tissue engineering.