Involvement of one or both gonads in postpuberty mumps is common and c
an often lead to infertility. Our report discusses the course of disea
se of a patient with acute mumps orchitis. Only 2 days after administr
ation of interferon, clinical symptoms had drastically improved, and t
he infection subsided without any after-effects. We therefore recommen
d immediate interferon therapy, as soon as postpuberty mumps manifests
, to prevent testicular atrophy and resulting infertility.