Four boys, aged 2 months, 1 month, 16 years and 17 years, presented with an acute painful swelling in the scrotum. Both newborns were considered to have an inguinal hernia, but one of them turned out to have a testicular torsion. Both adolescents, however, were assumed to have a testicular torsion, yet one of them had an incarcerated scrotal hernia. The diagnostic errors resulted in an orchidectomy in the newborn because of delayed operative intervention, while a second (inguinal) incision was required in the adolescent boy for the hernia repair. The other boys were treated appropriately immediately. The post-operative recovery was uncomplicated in all children. Although ultrasound may be valuable in the evaluation of the 'acute scrotum', it should not prevent or postpone prompt surgical exploration in boys with severe symptoms.