Using cadmium telluride (CdTe) as a detector, we assembled a computerized single probe system. The size of the CdTe used is 16 mm in diameter and 2 mm in thickness. Two types of the straight bore collimators of 16 mm in diameter were prepared. One is 16 mm in length (long type) and the other is 5 mm in length (short type) . The response curves of the long and short type collimators to57Co in water showed that the points at 10% of maximum counts were 4 cm and 3 cm in depth along the center axis. The data were accumulated by using a commercialized single cardiac probe system (OMNISCOFE) and processed by itself or transferred to the microcomputer (LSI-11/23) for further analysis. Twenty percent count loss occurred at 100000 cps with an integral discriminator setting. This system was applied for cerebrospinal fluid (CSF) shunt flow evaluation and measurement of left ventricular ejection fraction (LVEF) . Measurement of CSF shunt flow has been able to do in any patient's positioning. In 21 patients with various heart diseases, LVEFs obtained by CdTe detector were compared with those obtained by scintillation detector. There was good correlation between the LVEFs obtained by these two detectors: correlation coefficient (γ) =0.939.