A total of 215 animals of twelve inbred strains of mice (A.CA/W, AKR/W, BALB/cW, BN/aW,C57BL/6W, C57Bl/10W, CBA/W, CBAT6/W, C3H/W, DBA/2W, 129Sl/SvW and HLB/219J) bred at the Cancer Centre and Institute of Oncology, Warsaw (Oncology Centre), were characterized In terms of five blood serum biochemical indicators related to their health, reproduction and genetic background. Glucose, total protein, creatinine, triglycerides (triacylglycerols) and total cholesterol were determined in mice aged four months. Significant interstrain differences were found among nearly all parameters considered, with the exception of total protein. The level of triglycerides showed wide interstrain differences and revealed a similar variation trend as the total cholesterol.For cholesterol and triglycerides, significant differences between sexes for the majority of strains were found. The results obtained may be important in the selection of experimental animals,for analysis of changes associated with various diseases, and for the explanation of their genetic background.