A compact mouse MRI has been developed using a 1.0T yokeless permanent magnet and portable MRI console. The entire system was installed in a space measuring 2 m x 1 m. The imaging region was the cylindrical volume (35 mm diameter, 50 mm length) at the center of the magnet and was used for whole-brain or body imaging of mice. Whole-brain imaging took less than 90 min for T1- and T2-weighted 3D images with 2-mm slice thickness and 200-microm in-plane resolution. Body imaging took less than 30 min for T1-weighted spin-echo and FLASH 3D images with 0.5- to 1.0-mm slice thickness and 250- to 300-microm in-plane resolution. In addition to the compactness of the system, the mouse MRI has several advantages over high-field superconducting animal MRI systems in its accessibility to the specimen, similarity to clinical MRI in image contrast, capacity for biological isolation, and maintenance. The results obtained demonstrate the potential of this new system for routine imaging in biomedical laboratories.