Abstract Body: Background: Erectile dysfunction (ED) is largely associated with obesity, however, the consequences of early life obesity for ED in young adulthood are unknown. We hypothesize that obesity induced by preweaning overfeeding impairs vascular and erectile function and affects blood pressure in young adult male rats (5-month-old). Methods: At postnatal day (PND) 1, Wistar rats were divided into a normal litter (NL, 5 female + 5 male pups/dam) or small litter (SL, 2 male + 1 female pup/dam) during lactation. After weaning, SL pups had increased body weight. Next, rats from both groups returned to normal size colonies (4-5 rats per cage) and were fed standard chow. At PND160, we evaluated body weight and fat pad deposition, mean arterial pressure (MAP) by tail-cuff, and pudendal artery (PA) and corpus cavernosum (CC) reactivity. Concentration-response curves to phenylephrine (PE) or acetylcholine (ACh) were performed in both preparations. In the CC, contraction and relaxation to electrical field stimulation (EFS) were obtained. Concentration-response curves were analyzed using non-linear regression analysis. RNA sequencing (RNAseq) analyses were performed in both PA and CC. Data were analyzed by Student’s t-test and presented as mean ± S.E.M. Statistical significance was set at p<0.05. Results: At PND160 no differences in body weight were observed in SL (594±14g) compared to NL (559±13g), however, there was an increase in fat deposition in SL (retroperitoneal fat: NL 7.47±0.69g vs SL 11.25±1.23g; perigonadal fat: NL 10.05±0.55g vs SL 13.24±1.16g). MAP was higher in SL (120.5±1.20 mmHg vs 114.9±0.58 NL). In the PA, ACh-induced relaxation was reduced in SL (Emax: 28±6%) vs NL (Emax: 68±5.5%), with no changes in the contraction to PE. In the CC, EFS-induced relaxation was significantly decreased in SL rats compared to NL rats (16 Hz: NL 3.06 ± 0.28% vs SL 2.39 ± 0.53%). RNAseq revealed that, in PA from SL rats, 289 and 224 genes were down and upregulated, respectively, while in the CC from SL rats, 115 genes were downregulated, and 110 genes were upregulated. Among them, hcn2 gene (which encodes HCN2, the hyperpolarization-activated cyclic nucleotide-gated potassium and sodium channel 2) was strongly downregulated in both PA and CC, and this may affect mechanotransduction. Conclusion: Our data shows that early-life obesity causes long-lasting vascular and cavernous damage that might be associated with endothelial and erectile dysfunction in young adulthood.