tThe objective of this study was to evaluate the effects of dietary supplements ofrumen-protected folic acid (RPFA) on lactation performance, energy balance, reproductiveperformance and blood parameters of dairy cows. Ninety-six multiparous Holstein cowswere assigned to four groups of 24 each according to their previous 305-days milk produc-tion. The treatments were: control, low RPFA (LRPFA), medium RPFA (MRPFA) and high RPFA(HRPFA) with 0–3 g RPFA/cow per day, respectively. Supplements of RPFA were top-dressedand manually mixed into the upper one third of the ration during the morning feeding from3 weeks before the expected calving date to 15 weeks after parturition. Dry matter (DM)and net energy (NE) intakes, milk yield, milk protein content and production increasedlinearly (P < 0.05) with increasing RPFA supplementation, whereas milk fat content andproduction only tended to be linearly increased. Cows supplemented with RPFA showeda similar pattern (P < 0.05) of decreased loss of body weight (BW) and improved energybalance (expressed in MJ/cow/day) during the 105 days in milk (DIM) period. Concentra-tions of glucose in plasma, folate and methionine in serum increased linearly (P < 0.05),whereas concentrations of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA)and serum homocysteine linearly (P < 0.01) decreased. Total conception rate and the per-centage of cows pregnant at 150 DIM linearly increased (P < 0.05), DIM at first breedingand breeding per conception tended to change linearly with increasing RPFA supplemen-tation. These results indicated that supplementary RPFA in cow diets had positive effectson feed intake and milk production, increased concentrations of plasma glucose and serumfolates, decreased plasma concentrations of NEFA and BHBA and serum concentration ofhomocysteine, and improved energy balance and reproductive performance. These datasuggest that RPFA improves lactation, energy balance and reproductive performance in adose-dependent manner.