The purpose of this study was to evaluate 1/T 1 ρ in relation to 1/T 1 and 1/T 2 in characterizing normal and diseased muscle. We measured the muscle relaxation rates 1/T 1 and 1/T 2 at 0.1 T and 1/T 1 ρ at on-resonance locking fields B 1 between 10 and 160 μT in myositis patients and normal volunteers. 1/T 2 and 1/T 1 ρ of muscle were lower in the patients than in the volunteers, whereas there was no difference in the 1/T 1 values. The lower relaxation rates 1/T 2 and 1/T 1 ρ in the diseased muscle may be due to fat and connective tissue infiltrations and edema. 1/T 1 ρ contrast between muscle and subcutaneous fat was higher than 1/T 2 and 1/T 1 contrast. This may be explained by the different B 1 dispersion behavior of these two tissue types. 1/T 1 ρ of fat is B 1 field independent, whereas 1/T 1 ρ of muscle decreases clearly with increasing B 1 field. In conclusion, 1/T 1 ρ provides a useful tool in manipulating contrast in magnetic resonance imaging of diseased muscle.