The objective of this study was to establish and evaluate a new model for studying lipogenesis in grass carp preadipocytes. The morphology characteristic from preadipocytes to mature adipocytes was observed with the microscopic morphology, and the proliferation kinetics of cells was tested by cell counting. In addition, the nature and differentiation degree of cells were evaluated using Oil Red O staining, lipase activity determination, and reverse transcription PCR (RT-PCR) assay. Morphologically, grass carp preadipocytes started to attach and grow on day 3, then they resembled fibroblasts, and most underwent attachment, proliferation, and growth arrest with subsequent accumulation of intracellular lipid droplets before becoming mature adipocytes. Glycerol-3-phosphate dehydrogenase (GPDH) activity was increased gradually during the progress of culture. Analysis of RT-PCR confirmed that peroxisome proliferator-activated receptor-γ expression patterns were consistent with my observations regarding GPDH activity. In summary, grass carp preadipocytes cultured with 10% FBS at 28°C in a humidified 5% CO2 atmosphere have high proliferation potential. Furthermore, the cells synthesize a range of markers that are consistent with this cell type. We conclude therefore that the grass carp preadipocytes described here have high capacity for lipogenesis and may, therefore, represent a unique tool for studying fish fat cell development and metabolism.