Many authors consider the Lymphogranuloma venereum as an infectious disease caused by virus invading the whole organism, including the nervous system. In these cases, the cerebrospinal fluid examination is very helpful, but the studies accomplished are not satisfactory. That is why we did some research work. We got together 68 patients presenting this disease. The cerebrospinal fluid tests were made in all phases of the illness: we examined the cerebrospinal fluid of 9 asymptomatics patients, 7 with initial chancre, 3 with inguinal buboes, 30 with proctitis without stricture, 8 with both stricture and proctitis, 4 with stricture and proctitis and fistulas, 5 with esthiomene, 1 with stricture without proctitis and 1 with balanitis. All these patients did not present clinical symptomatology of meningoencephalitis, but only slight symptoms such as irritability, headache or other pains were observed in some of them. The cerebrospinal fluid was normal in 63 patients. In the 5 remaining cases we found slight changes of the fluid: a) hyperglycorrhachia in one case (0,98 g. °/oo) ; b) pleocytosis in two cases (15 cells per mm³, in one case and 7 cells per mm³ in another one) both luetic patients; c) pressure increase (270 mms. of water) in one patient with cardiovascular disorders; d) transitory pleocytosis, without any apparent cause than the Nicolas-Favre disease. In this series of 5 cases, only one (transitory pleocytosis) may be perhaps due to Lymphogranuloma venereum. Our studies do not confirm the investigations of those who often verified cerebrospinal fluid changes in patients presenting Nicolas-Favre disease, but free of serious clinical nervous symptoms.