Modulation transfer functions, line spread functions, and energy spectra were obtained for an Anger scintillation camera using three different collimators and commercially produced 201Tl. Images of a thyroid phantom were obtained using these collimators. For each of the three collimators, line spread functions and modulation transfer functions were obtained for both the 75-keV x-ray and 167-keV gamma photon of 201Tl. Although the intrinsic resolution of the scintillation camera is superior when imaging with the 167-keV gamma photon, system performance was superior when the 75-keV x-ray was imaged. Contamination form 202Tl, which emits abundant 439-keV gamma photons, degraded images taken at 167 keV because of septum penetration. At 75 and 167 keV the converging collimator yielded the best system performance. Imaging time was significantly shorter using the 75-keV x-rays.