Substantial data suggest that elevated triglycerides are associated with increased coronary risk, and may be an independent coronary risk factor. Although it is generally accepted that patients with hypertriglyceridemia can have marked improvement in lipids after vigorous nonpharmacologic therapy, data to support this belief are lacking. This study assessed 313 consecutive patients before and after outpatient phase II cardiac rehabilitation and exercise programs to compare the response of patients with elevated triglycerides (> or = 250 mg/dl; n = 39) to vigorous nonpharmacologic therapy with the response of patients with "normal" triglyceride levels (< 150 mg/dl; n = 157). The independent effects that baseline triglycerides, as well as other variables, had on improving lipids after nonpharmacologic therapy were also determined. After cardiac rehabilitation and exercise training, patients had improvement in total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol levels, low-density lipoprotein (LDL) cholesterol levels, LDL/HDL ratios, body mass index, percent body fat, and METs. Patients with hypertriglyceridemia were younger (p = 0.05) and had higher baseline body mass index (p < 0.001) and LDL/HDL ratios (p < 0.0001) but lower HDL cholesterol levels (p < 0.0001) than patients with low baseline triglycerides. Both groups had improvement in lipids, obesity indexes, and exercise capacity. However, patients with hypertriglyceridemia had significantly greater reductions in triglycerides (-31% vs +3%; p < 0.0001), but had less improvement in both LDL cholesterol levels (0% vs -4%; p < 0.01) and LDL/HDL ratios (-5% vs -9%; p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)