Staging and therapy monitoring of malignant lymphomas relies heavily on imaging using arbitrary size criteria from computed tomography (CT) and sometimes non-specific radionuclide studies to assess the activity of the disease. Treatment decisions are based on early assessment of the response to therapy and the residual volume of the disease. Our initial experience is reported using a new noninvasive, inexpensive, and reproducible passive imaging modality, Dynamic Infrared Imaging (DIRI), which may add a new dimension to functional imaging. This system relies on its ability to filter the raw infrared signal using biological oscillatory behavior. It detects and analyzes minute oscillations of temperature and heat distribution in tumors.