Abstract: An ambulatory physiological monitor includes an input for receiving physiological data such as electrocardiography (ECG) data from a patient. This data is transferred to a disk drive by a processor or other suitable hardware. The disk drive records this data on the disk recording medium. The data is stored in noncompressed form. Preferably, to conserve power in the monitor, a buffer is also provided. The buffer temporarily holds the incoming data until the buffer is full. When the buffer is full, the disk drive is activated, and the contents are forwarded to the disk drive for storage on the disk recording medium. The monitor is switched from a low resolution mode to a high resolution mode in response to activation of an event button or at predetermined intervals.