This is a randomized, double-blind, placebo-controlled, dose-ranging, multi-center study. Following a 6-8 week placebo and dietary-controlled baseline period, approximately 195 men and women with either hypertriglyceridemia or mixed hyperlipidemia with serum triglycerides (TG) > 200 mg/dl (2.26 mmol/l) will be randomized to receive either placebo, 30 mg TRIA-662 or 90 mg TRIA-662 three times daily for twelve weeks. Lipid and ancillary exploratory parameters will be evaluated at screening, during the baseline period, upon randomisation and throughout the 12-week active treatment period.