Liraglutide is a new glucagon-like peptide-1 (GLP-1) receptor agonist and a true GLP-1 analogue. After successful phase 2 studies, liraglutide was assessed in a series of phase 3 trials [(Liraglutide Effect and Action in Diabetes (LEAD)] designed to demonstrate efficacy and safety across the continuum of type 2 diabetes antihyperglycaemic care, both as monotherapy and in combination with commonly used oral antidiabetic drugs (OADs). The LEAD programme also compared liraglutide with other OADs. As a monotherapy, liraglutide demonstrated significant improvements in glycaemic control in comparison with glimepiride. When combined with one or two OADs, reductions in haemoglobin A1c, fasting plasma glucose and postprandial glucose were generally greater with liraglutide than with comparators. Throughout the trials, liraglutide was associated with weight reduction; in most instances, the reduction from baseline was significantly greater than that seen with comparators. Improvements in assessments of beta-cell function were consistently shown with liraglutide treatment across all trials. Furthermore, reductions in systolic blood pressure were reported. Liraglutide was associated with a low risk of hypoglycaemia and was generally well tolerated. The majority of adverse effects were gastrointestinal, the most frequent of which was nausea.