SummaryA large group of related benzo(b)thiophene derivatives was screened for antiviral activity in a simple cell culture system. Three viruses were used; influenza A2, vaecinia and herpes simplex type 1.51 per cent of the compounds inhibited at least one virus by >75 per cent, while 25 per cent were inhibitory by >90 per cent. This high degree of antiviral activity is in agreement with the range of biological properties possessed by benzo(b)thiophene derivatives as a whole.