The most energy-requiring organ in the body, the cardiac muscle, relies primarily on lipoprotein-derived fatty acids. Prenatal loss of cardiac lipoprotein lipase (LPL) leads to hypertriglyceridemia, but no cardiac dysfunction, in young mice. Cardiac specific loss of LPL in 8-wk-old mice was produced by a 2-wk tamoxifen treatment of MerCreMer (MCM)/Lpl^flox/flox mice. LPL gene deletion was confirmed by PCR analysis, and LPL mRNA expression was reduced by ∼70%. One week after tamoxifen was completed, triglyceride was increased with LPL deletion, 162 ± 53 vs. 91 ± 21 mg/dl, P < 0.01. Tamoxifen treatment of Lpl^flox/flox mice did not cause a significant increase in triglyceride levels. Four weeks after tamoxifen, MCM/Lpl^flox/flox mice had triglyceride levels of 190 ± 27 mg/dl, similar to those of mice with prenatal LPL deletion. One week after the tamoxifen, MCM/Lpl^flox/flox, but not Lpl^flox/flox, mice had decreases in carnitine palmitoyl transferase I mRNA (18%) and pyruvate dehydrogenase kinase 4 mRNA (38%). These changes in gene expression became more robust with time. Acute loss of LPL decreased ejection fraction and increased mRNA levels for atrial natriuretic factor. Our studies show that acute loss of LPL can be produced and leads to rapid alteration in gene expression and cardiac dysfunction.