A description is made of the diagnosis of cases of abortion, neonatal foal death and nervous system disorders caused by equine herpesvirus type 1 (EHV-1) in 1999, carried out in the Laboratory of Virology at the Faculty of Veterinary Medicine in Merelbeke, Belgium. Twenty-eight cases originated from Flanders, two from Wallonia and one from the Netherlands. There were 22 abortions, four neonatal foal deaths and five cases of nervous system disorders. The diagnosis was made by means of virus isolation. Twenty-nine percent of the horses involved had been vaccinated against EHV-1.