Hypertriglyceridaemia (typical triglyceride level 1.7–5.0 mmol/l) is caused by interactions between many genetic and nongenetic factors, and is a common risk factor for atherosclerotic cardiovascular disease (CVD). Patients with hypertriglyceridaemia usually present with obesity, insulin resistance, hepatic steatosis, ectopic fat deposition, and diabetes mellitus. Hypertriglyceridaemia reflects the accumulation in plasma of proatherogenic lipoproteins, triglyceride-rich lipoprotein (TRL) remnants, and small, dense LDL particles. Mendelian randomization studies and research on inherited dyslipidaemias, such as type III dysbetalipoproteinaemia, testify that TRLs are causally related to atherosclerotic CVD. Extreme hypertriglyceridaemia (a triglyceride level >20 mmol/l) is rare, often monogenic in aetiology, and frequently causes pancreatitis. Treatment of hypertriglyceridaemia relies on correcting secondary factors and unhealthy lifestyle habits, particularly poor diet and lack of exercise. Pharmacotherapy is indicated for patients with established CVD or individuals at moderate-to-high risk of CVD, primarily those with metabolic syndrome or diabetes. Statins are the cornerstone of treatment, followed by fibrates and n-3 fatty acids, to achieve recommended therapeutic levels of plasma LDL cholesterol, non-HDL cholesterol, and apolipoprotein (apo) B-100. The case for using niacin has been weakened by the results of clinical trials, but needs further investigation. Extreme hypertriglyceridaemia requires strict dietary measures, and patients with a diagnosis of genetic lipoprotein lipase deficiency might benefit from LPL gene replacement therapy. Several therapies for regulating TRL metabolism, including inhibitors of diacylglycerol O-acyltransferase and microsomal triglyceride transfer protein, and apoC-III antisense oligonucleotides, merit further investigation in patients with hypertriglyceridaemia.