The aim of this study was to investigate the effect of intratesticular local anesthesia on weight gain and behavioral and cortisol changes in piglets submitted to castration. Study design was a randomized controlled trial. Twenty-nine male Landrace crossbred piglets aged 3 to 6 days were used. The piglets were randomly divided into two groups: orchiectomy with anesthesia (A, n = 15) and orchiectomy without anesthesia (NOA, n = 14). Piglets in the A and NOA groups were treated with 0.5 mL of intratesticular 2% lidocaine with a vasoconstrictor in each testicle and 0.5 mL of intratesticular 0.9% sodium chloride, respectively. Blood samples were collected from all animals immediately after surgery and at 3 and 6 days postoperatively for measurement of the serum cortisol concentration. Behavior was assessed daily for 6 days by two observers blinded to the treatment. Weight was measured at the same time as cortisol measurement. Analysis of variance followed by the Student-Newman-Keuls test was used to investigate differences in time within and between the two groups. Mean times of six evaluations done for 90 minutes during 6 days of each behavior were compared by Tukey t test. The level of statistical significance was 5%. The serum cortisol concentration was higher immediately after surgery than at 3 and 6 days postoperatively in both groups. Weight gain was greater at 3 and 6 days postoperatively in the A group than in the NOA group. Intratesticular local anesthesia before castration in piglets is technically practical, is in accordance with good welfare practice, and improves short-term weight gain in piglets submitted to castration. Key words: Behavior. Castration. Lidocaine. Pig. ResumoO objetivo deste estudo foi investigar o efeito da anestesia local intratesticular prévia à castração sobre o ganho de peso, comportamento e alterações no cortisol de leitões. O delineamento experimental adotado foi inteiramente casualisado. Foram utilizados vinte e nove leitões mestiços Landrace -Large White do sexo masculino com idade de 3 a 6 dias. Os leitões foram divididos aleatoriamente em dois grupos: orquiectomia com anestesia (A, n = 15) e orquiectomia sem anestesia (NOA, n = 14). Aos leitões do grupo A foi administrado 0,5 mL de lidocaína 2% intratesticular com vasoconstritor em cada testículo, e no grupo NOA administrou-se 0,5 mL de NaCl 0,9% intra testicular também em cada testículo. Amostras de sangue foram coletadas de todos os animais imediatamente após a cirurgia e posteriormente aos 3 e 6 dias após a cirurgia para a medição da concentração de cortisol sérico. O comportamento foi avaliado diariamente durante 6 dias por dois observadores que desconheciam o tratamento. O peso foi medido ao mesmo tempo que o cortisol sanguíneo. Foi realizada a análise de variância, e o teste Student-NewmanKeuls para contraste entre médias. O tempo médio de seis avaliações realizadas por 90 minutos durante 6 dias para cada comportamento foi comparado pelo teste de Tukey. O nível de significância estatística foi de 5%. A concentra...