This trial was conducted to study the alleviation effects of L-arginine on intrauterine growth retardation (IUGR) of fetal pigs induced by NG-nitro-L-arginine methyl ester (L-NAME) challenge. Forty Landrace×Large Yorkshire pregnant sows ranged from the second to the forth parity and with similar expected date of delivery were randomly divided into 4 treatments (treatments Ⅰ, Ⅱ, Ⅲ and Ⅳ) with 10 replicates per treatment and 1 sow per replicate, representing positive control, negative control, L-NAME+1.0% L-arginine and 1.0% L-arginine, respectively. From d 85 to d 105 of gestation, gilts in treatments Ⅱ (negative control) and Ⅲ were subcutaneously injected with 2.5 mL L-NAME (15.0 mg/kg BW) in the neck and back every day in order to induce IUGR, and the gilts in treatments Ⅰ (positive control) and Ⅳ were injected the same volume of physiological saline with the same method. The serum from auricular vein at d 85 and 105 of gestation and from blood vessels of placenta of sows after farrowing were collected, and nitrogen monoxide (NO) and total nitric oxide synthase (TNOS) was then determined. The total piglets born per litter, total piglets born alive per litter, birth weight of all piglets born, birth weight of all piglets born alive, litter birth weight of all piglets born, as well as litter birth weight of all piglets born alive were recorded after farrowing, and the IUGR incidence was then counted. The results showed as follows: 1) the total piglets born alive per litter (12.60 vs. 11.20, P<0.05) and the litter birth weight of all piglets born alive (18.26 vs. 16.21, P<0.05) were greater for the 1.0% L-arginine group compared with the positive control, and the IUGR incidence decreased from 17.49% to 6.35% (P<0.05). 2) Compared with the control group, the total piglets born alive per litter and the litter birth weight of all piglets born alive of sows injected with L-NAME (treatment Ⅱ) were reduced by 19.64% (P<0.05) and 27.14% (P<0.01), respectively. Meanwhile, the IUGR incidence was increased to 34.49% (P<0.01). However, 1.0% L-arginine recovered the total piglets born alive per litter and the litter birth weight of all piglets born alive for sows injected with L-NAME to the normal level, and no significant difference in IUGR incidence was observed between the positive control group and the L-NAME+1.0% L-arginine group (P>0.05). 3) Yields of NO and TNOS in blood vessels of placenta were significantly reduced after injection with L-NAME (P<0.01). However, yields of NO and TNOS were recovered to the normal level when 1.0% L-arginine was supplemented to the diets. In conclusion, 1.0% L-arginine supplemented to the diets of pregnant gilts could counteract intrauterine growth retardation induced by L-NAME challenge, enhance the growth and development of fetal pigs, and decrease the IUGR incidence.［Chinese Journal of Animal Nutrition, 2010，22（4）:879-885］