High resolution images can be obtained from anywhere in the body of small animals with magnetic resonance combined with cardiac gating and scan synchronous ventilation. We used these methods to examine the intrathoracic anatomy of the rat. Anesthetized rats were intubated and ventilated in synchrony with imaging acquisition. Images were obtained in a 1 m bore, 1.5 T system fitted with a 28 cm diameter high field gradient coil and a 5 cm radio-frequency coil. We used cardiac gated, three-dimensional spin warp acquisitions. Eight contiguous slices (2.5 mm thick) were obtained simultaneously. In addition to visualizing major vessels and cardiac chambers, cardiac valves and papillary muscles were clearly demonstrated. Major pulmonary vessels and peripheral parenchyma were also seen. These results demonstrate MR "microscopy" can be used to image all major cardiopulmonary structures in the rat with respect to selected times of the cardiac cycle. This capability for noninvasive "microscopy" opens new avenues for cardiopulmonary research using well characterized rodent models.