Objective To compare the disparity of nine isozymes in SPF and conventional rabbits,and to provide evidence for analyzing the influence of different genic background of rabbits on pyrogen test experiments.Methods Isozyme electrophoresis on cellulose acetate membrane method was used to detect 9 biochemical loci(such as ADH,etc.)in 40 conventional(from Beijing)and 40 SPF rabbits(from Shanghai).Results There were polymorphisms at 6 loci(such as ADH,etc).There were two differences between the SPF and conventional New-Zealand rabbits:at Gpd1 loci SPF rabbits did not have c gene,while conventional rabbits had c gene;at Idh1 loci SPF did not have ab gene,while there was c gene in the conventional rabbits.The single gene frequency at 3 loci ES,GPD-1 and MPI-1 was 82.5%(Esb),88.75%(Gpd-1a)and 70.%(Mpi-1a),respectively.Conclusion Since the considerable difference in gene polymorphisms and gene frequency between SPF and conventional rabbits,we would suggest that attention should be paid to select appropriate rabbit population and to consider the influence of decrease of gene polymorphisms in SPF rabbits on experiments such as pyrogen tests.