In vitro studies were initiated to determine the suitability of murine and rat macrophages as delivery vehicles for gold nanoshells in the treatment of gliomas. Visualization of macrophage accumulation in and around gliomas may be accomplished using magnetic resonance imaging (MRI) and superparamagnetic iron oxide nanoparticles (SPIO). The optimal loading of both murine and rat macrophages with SPIO was determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Higher concentrations of SPIO were observed in rat macrophages and the optimal concentration in these cell lines was around 300 μg/ml. Higher concentrations resulted in significant cell toxicity. SPIO were visualized in fixed rat brains subjected to high field MRI using T 2*-weighted gradient echo pulse sequences. Macrophages were found to be very sensitive to near infra-red (NIR) laser irradiation.