To evaluate the value of "low-signal zone" sign in the diagnosis of brain abscess in the capsule period.The conventional MRI was performed pre-therapy in 21 patients with brain abscess in the capsule period and 25 patients with vesica-astrocytomas. We analyzed the pathologic basis of "low-signal zone" sign in brain abscess and compared the frequency and shape of "low-signal zone" sign in brain abscess and vesica-astrocytomas.The "low-signal zone" sign in MRI occurred more frequently in brain abscess (85.7%, 18/21) than in vesica-astrocytomas (52.0%, 13/25). The "low-signal zone" sign in the former was intact, while that in the latter was not.The "low-signal zone" sign is helpful to diagnose brain abscess in the capsule period, and is valuable to differentiate brain abscess and vesica-astrocytomas.