Lipoprotein lipase (LPL) is a key enzyme involved with hydrolysis and removal of triglycerides from plasma. LPL deficiency is a rare condition with an estimated prevalence of 1 in 106. It is characterized biochemically by elevated triglycerides and lowered HDL in the plasma and clinically by a constellation of signs and symptoms during childhood including failure to thrive, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly, and acute pancreatitis. Nearly 100 mutations in the LPL gene have been associated with LPL deficiency. Here we report 2 unrelated pedigrees with LPL deficiency from 2 novel disease-causing LPL mutations: a Gly159Glu missense mutation in exon 5 and a 4-bp ACGG deletion at the 3' boundary of exon 2. We present molecular findings of these 2 cases and review the biochemical, clinical, and genetic features of LPL deficiency.