Biomarkers are not established for cardiovascular phenotyping in mice. We compared the use of echocardiography with the determination of N-terminal propeptide of the atrial natriuretic peptide (Nt-proANP) and osteopontin (Opn). We measured plasma Nt-proANP and Opn levels in (1) the inbred strains C57BL/6, BALB/c, C3H/He, DBA/2, FVB/N, 129S1/Sv; (2) a surgical model of nonischemic myocardial infarction; and (3) delta-sarcoglycan (Sgcd) and calsarcin 1 [also known as myozenin 2 (Myoz2)] knockout models of cardiomyopathy. Left ventricular function was assessed as fractional shortening (FS) by echocardiography in conscious mice. Plasma Nt-proANP exhibited marked variability and ranged from 0.31 +/- 0.19 (C57BL/6 male mice) to 1.34 +/- 0.43 nmol/l (DBA/2 female mice), depending on sex, age, and genetic background. Opn was less variable than Nt-proANP and was decreased significantly in C3H/He and DBA/2 throughout the 16 wk of study. Nt-proANP increased temporarily in mice with myocardial injury. In contrast, Opn increased in both operated and sham-treated mice. Nt-proANP was inversely correlated with FS and distinguished controls from Sgcd and Myoz2 mutants with 100% sensitivity and 71% specificity. Opn was increased in Sgcd mutants, which exhibited only mildly reduced FS but marked myocardial degeneration and fibrosis. Both of these histologic features were absent in Myoz2 mutants. Nt-proANP is an early marker of cardiac disease and is suitable for age- and sex-matched comparisons between groups of transgenic and matched control mice. Opn is useful to detect inflammatory and degenerative myocardial disorders that may be missed by echocardiography.