Formation of collagen-apatite composite by biomimetic methods without any previous treatment of the collagen fibrils has been investigated. Reconstituted collagen fibrils obtained from Type I collagen solution were incubated in conventional and revised simulated body fluid (C and R-SBF) solutions to form calcium phosphate. Spherical deposits of B-type carbonate apatite started precipitating along the fibrils from day I of incubation in both C and R-SBF. But the large number of carbonate ions in R-SBF has changed the microstructure of the apatite precipitates. The calcium rich apatite deposits are more in R-SBF than in C-SBF. Percentage of Cl- ions in the precipitates of R-SBF were less than in C-SBF.