Lipoprotein lipase (LPL, triacylglycerol acylhydrolase; EC 3.1.1.3) deficiency (OMIM 238600) is an autosomal recessive inherited condition caused by mutations in the LPL gene, either in a homozygous or in a compound heterozygous state, leading to loss of lipolytic activity and resulting in severe hypertriglyceridaemia and subsequent risk for developing pancreatitis. Numerous LPL gene mutations leading to loss of catalytic function have been described. In this present study, we describe full clinical, biochemical and molecular analyses of severe hypertriglyceridaemic individuals in one Turkish and three Chinese families. We established one novel mutation (delCT1312-1313), a new combination of mutations (S193R and I194T) and four previously reported mutations (L252R, L252V, S193R and I194T) of the LPL gene and report phenotypes for these and four previously described mutations. Finally, we show that two patients homozygous for the LPL gene delCT1312-1313 mutations are characterized by absence of LPL activity that coincides with absence of LPL protein.