Cabergoline (CAB) is a long-acting dopamine agonist. In the first national study with CAB--as part of an international multicentric study--39 adult and adolescent females (16 to 44 years old) with hyperprolactinemic amenorrhea (18 microadenomas and 21 idiopathic hyperprolactinemias) were evaluated. CAB or bromocriptine (BEC) was administered for 24 weeks: over 8 weeks, treatment was given under double-blind conditions, and over the remaining 16 weeks (open period) 18 patients received CAB and 21 received BEC as a result of a random distribution. Maximum dosage: CAB = 1.5 mg in 2 or 3 weekly doses; BEC = up to 10 mg in 2 daily doses. Prolactin was measured at base line and 2, 4, 6, 8, 12, 14, 16, 20 and 24 weeks after the initiation of treatment. When vaginal bleeding was restored, progesterone was measured as an ovulation sign. The 4 adolescents continued with CAB treatment for 1 more year. Prolactin was statistically evaluated according to Man Whitney Test (general population) or Wilcoxon Test (adolescents). There were no significant differences between basal levels of prolactin (ng/ml) in patients treated with BEC or CAB: (173.86 +/- 28.23 and 152.11 +/- 14.06 respectively); at the fourth week of treatment the decrease was smaller (p = 0.005) in patients treated with BEC (36.36 +/- 5.71) than in those treated with CAB (14.06 +/- 3.60) and at 24 weeks differences disappeared: BEC = 19.88 +/- 4.48 and CAB = 9.63 +/- 2.62 (p = NS). The adolescents showed a marked decrease in prolactin with no significant differences between BEC and CAB: basal levels = 168.17 +/- 75.47 and 213 +/- 96.99 (p = NS); 4 weeks = 48.00 +/- 8.72 and 35.00 +/- 12.58 (p = NS); 24 weeks = 34.33 +/- 10.17 and 21.75 +/- 7.23 respectively. At 48 weeks (23.25 +/- 11.23) levels remained the same as those of week 24 (p = NS). Some patients treated with BEC had nausea, vomits and epigastralgia; these symptoms were not observed with CAB. All patients resumed menstrual cycles, except one treated with BEC; 6 patients treated with CAB became pregnant, and the 5 patients who continued under our control gave birth to healthy infants. It is concluded that CAB is a useful therapy. This is specially true for adolescents (an age group difficult to manage) because of its easy administration and the almost complete absence of side effects.