Focal brain lesions in AIDS may be difficult to diagnose with conventional imaging techniques. Recent advances in magnetic resonance (MR), including MR spectroscopy (MRS) and diffusion-weighted imaging (DWI), may provide additional information in the evaluation of these diseases. MRS of various AIDS brain lesions show distinct chemical profiles; however, several factors such as location of the voxel, echo time of the study, and disease stage, all have to be taken into consideration when interpreting the results of MRS. DWI demonstrates molecular motion within the tissue and may provide information regarding tissue integrity associated with various disease processes.