A telemetry capsule system was designed and implemented to measure the slow wave activity of the small bowel, which is an important parameter for the diagnosis of gastric diseases. The capsule amplified the slow wave signal from the intraluminal electrodes, and transmitted the digitally sampled data by means of a radio frequency transmitter. The implemented capsule (11 x 21 mm(2)) was smaller than a commercially available capsule endoscope, and it can remain active for more than 18 h. The feasibility of using this capsule was investigated by conducting in vitro experiments, and the average motility signals of the ileum, jejunum, and colon were measured as 6.1, 10.2, and 1.5 cycles per minute, respectively.