SummaryThree cases of serous tuberculous meningitis in adult patients with active pleuro-pulmonary tuberculosis are reported. In two of them tubercle bacilli were found on direct smear of spinal fluid.Several similar cases were previously described in the literature. The pathogenesis is briefly discussed. In the first stages the diagnostic may be very difficult, but the chemistry of spinal fluid could be of some help.Severe pronostic in the future allowed discussion of opportunity of streptomycin treatment.