[B28 Asp]-human insulin (insulin aspart, CAS 116094-23-6, X14) is a rapidly absorbed analogue of human insulin currently undergoing development for the treatment of diabetes mellitus. Cardiovascular studies and a range of standard behavioural, neurological and organ function tests were conducted in various animal species to investigate potential secondary pharmacological effects of insulin aspart. Single intravenous injections (to ensure maximum bioavailability) of a range of doses of insulin aspart were compared with a soluble human insulin preparation. The validity of the test systems was always tested with appropriate positive and/or negative (vehicle) control compounds. Secondary effects due to hypoglycaemia were identified by simultaneous administration of a glucose solution along with the highest dose of insulin aspart and the vehicle as negative control. No safety issues were raised by these experiments; insulin aspart and soluble human insulin exhibited similar pharmacological profiles throughout.