One of the key technologies for regenerations of damaged and lost tissues is the controlled release of biologically active growth factors. The present study was undertaken to investigate sorption and desorption of various biologically active growth factors from hydrogels prepared through glutaral dehyde crosslinking of gelatin with isoelectric points (IEPs) of 5.0 and 9.0, which are named “acidic” and “basic” gelatins, respectively, because of their electric feature. In the present study, basic fibroblast growth factor (bFGF), transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), and bone morphogenetic protein-2(BMP-2) were employed as growth fac tors, because their expected biological functions seem to be closely related to clinical applications. Basic bFGF and TGF-β1 were well sorbed with time to the acidic gelatin hydrogel, while less sorption was observed for the basic gelatin hydrogel. This can be explained in terms of the electrostatic interaction between the basic growth factors and acidic gelatin. However, VEGF and BMP-2, though their IEPs are higher than 7.0, were sorbed to the acidic gelatin hydrogel to a less extent than the two other factors. An in vivo experiment revealed that the hydrogels were degraded with time. The growth factors were retained in the body for a longer time period with their increasing sorption in vitro to the acidic gelatin hydrogel A correlation of the in vivo retention between the growth factor and hydrogel suggested that the basic growth factor ionically complexed to the acidic gelatin hydrogel was released in vivo as a result of hydrogel degradation.