Since the introduction of the mumps vaccine, the age of appearance of mumps infection has shifted from children to adolescents and young adults, groups with a higher incidence of disease complications and sequelae. During the years 2000-2001, the Gran Canaria Island was part of an epidemic of mumps. In that period, our institution attended 67 cases of serologically confirmed acute mumps orchitis, the most serious complication of mumps infection in young postpubertal males. We conducted a descriptive and prospective study of this cohort and extensively reviewed the literature from 1967 (the year the first mumps vaccine was introduced) to 2009. Fifty-six patients were admitted because of general impairment and were treated with alpha-interferon. Sixty-six patients presented parotitis previous to orchitis (interval from parotitis to orchitis, 4.9 d). Orchitis was unilateral in 89.5% and bilateral in 10.4% of cases. More than 98% of patients had orchitis-associated fever. Nine patients had clinical and biochemical data showing acute mumps meningitis, and 11 had subclinical pancreatitis. The mean duration of symptoms was 4.6 days (range, 1-9). During the acute phase, more than 41% of the evaluated testes had a volume >25 mL. Acute hormonal disturbances were highly prevalent. These included decreased levels of testosterone and inhibin B with low or normal levels of gonadotropins in 35% of subjects, and, to our knowledge not previously reported, an atypical hormonal pattern consisting of low levels of free testosterone and inhibin B, along with increased measures of luteinizing hormone but low or normal follicle-stimulating hormone levels (11% of cases). During the follow-up period (mean, 331 d) a high incidence of sperm disturbance was found.