The nitroblue tetrazolium test, although unespecific, seems to be useful to ease the differential diagnosis of several affections, specially in indicating wheter a given illness is of a presumably bacterial nature. Consequently, it is worth testing it in diseases of different origin. We carned out here an investigation in cases of acquired toxoplasmosis, lymphadenopatic form. Twenty-six cases were studied and the obtained values ranged from 6% ou 50%, but usually over 17% during course of the disease up to four months of duration, the starting date being the beginning of clinicai symptoms. In cases of longer course the obtained figures were usually lower than 17%. There was no simultaneous disease in the studied group, thereby disclosing any false positive result.