Productivity of Simmentaler heifers, first mated at 14 months of age (2 M) compared to the traditional system of mating at 26 months of age (3 M), was investigated under extensive farming conditions. Both first calving (60.8 vs. 79.5%) and recalving rates (42.4 vs. 71.2%) differed (P < 0.01) between 2 M and 3 M heifers, respectively. Although total number of calves born (4.0 vs. 3.2) and weaned (3.3 vs. 3.1) over seven years differed (P≤ 0.05) between 2 M and 3 M, total weaning weight (669 vs. 645 kg) was not significantly (P > 0.05) influenced. Also, 18.6% of all calves born in 2 M, died at birth. It is concluded that improved productivity is unlikely in an early mating system without additional inputs.