Brazil. Supervised all phases of the study; conception, design, intellectual and scientific content of the study; manuscript writing; critical revision. ABSTRACT PURPOSE:To evaluate the effects of aspirin 10% and 20% on mesenteric lymph nodes of rabbits as basis for its use on lymph nodes metastases. METHODS: A total of 20 lymph nodes from 20 rabbits (randomized in four groups) were evaluated. Aspirin solutions 10% (groups A and C) and 20% (groups B and D) were injected into mesenteric lymph nodes of healthy rabbits and had its gross and histological effects evaluated at 24 hours (groups A and B) and at seven days (groups C and D). RESULTS:In the groups A and B evaluated at 24 hours it was observed extensive necrosis and hemorrhage, a significant increase in apoptosis throughout the lymph node with medullary sinuses enlargement and an increase in germinal centers. In the groups C and D evaluated at seven days of solution injection there was also an increase in apoptosis with higher elevation of histiocytes and a significant decrease of necrosis and an increase of giant cells was noticed causing a foreign body chronic inflammation. In all comparisons, there were no differences between the concentrations used (10 and 20%). CONCLUSIONS: The injection of aspirin on lymph nodes caused necrosis and an increase of apoptosis after 24 hours and after seven days of treatment there was regeneration of the lymph nodes, with intense decrease of necrosis and a great elevation of apoptosis. These experimental results support future clinical studies on application of aspirin in the treatment of lymphatic metastases, since the increase of apoptosis is one of the pillars of cancer therapy. Key words: Aspirin. Lymph Nodes. Neoplasm Metastasis. Apoptosis. Therapeutics. Rabbits. RESUMOOBjETIvO: Avaliar os efeitos do ácido acetilsalicílico a 10% e 20% em linfonodos mesentéricos de coelhos para posterior embasamento e uso em metástases linfonodais. MéTODOS: Um total de 20 linfonodos de 20 coelhos (divididos aleatoriamente em quatro grupos) foi avaliado. As soluções de aspirina a 10% (grupos A e C) e 20% (grupos B e D) foram injetadas em linfonodos mesentéricos de coelhos sadios e seus efeitos macroscópicos e histológicos foram avaliados em 24 horas (grupos A e B) e em sete dias (grupos C e D). RESULTADOS: Nos grupos avaliados em 24 horas (A e B) foi verificada intensa necrose e hemorragia, aumento importante de apoptose em todo o linfonodo, com alargamento dos seios medulares e aumento dos centros germinativos. Nos grupos avaliados em sete dias (C e D) também houve aumento da apoptose, com maior elevação de histiócitos e diminuição importante da necrose; a hemorragia foi ausente e aumento de células gigantes foi visualizado, conferindo processo inflamatório crônico do tipo corpo estranho. Não houve diferença entre as concentrações utilizadas (10 e 20%) em nenhuma das comparações. CONCLUSÕES: A injeção de aspirina em linfonodos causou necrose e um aumento de apoptose após 24 horas e após sete dias de tratamento, houve regeneração dos g...