Computed tomography (CT) is a sensitive noninvasive study used for the diagnosis of cerebral lesions in patients with AIDS. Toxoplasmosis is, by far, the most common opportunistic central nervous system disease (CNS) in this population; accordingly, most groups start empirical antitoxoplasma therapy if the radiological features of the lesion suggest the diagnosis. It is common, however, when CT images do not suggest toxoplasmosis, not to start empirical therapy until the investigation of the lesion with other studies has not been completed. We report a case of cerebral toxoplasmosis in a patient with AIDS which, in our opinion, illustrates that empirical antitoxoplasma therapy should be started in all CNS lesions in patients with HIV infection while etiological investigation is undertaken, independently from the appearance of the lesion in the CT.