The validity of a new noninvasive device, the cardiokymograph, was assessed as to its ability to detect regional myocardial wall motion by direct comparison of the analog tracing with that of an epicardial length gauge in 11 open-chest dogs. The correlation of the two methods was excellent both during control conditions and following changes induced by acute coronary occlusion. The average difference between the methods in timing of various cardiac events was only 6.2 +/- 1.9 ms at rest and 6.8 +/- 1.5 ms following ischemia (P = NS). Relative amplitude ratio correlations, determined for the four portions of the cardiac cyele (isovolumic systole, ejection, isovolumic relaxation, and diastole), were also excellent. The average correlation of the kymograph to the length gauge was r = 0.896 +/- 0.018 at rest (K = 0.977 LG + 0.033) and r = 0.932 +/- 0.013 following occlusion (K = 1.071 LG + 0.101). Thus, the cardiokymograph is a sensitive and accurate noninvasive method for detection of regional ischemic dysfunction and produces an analog tracing essentially identical to that of the epicardial length gauge.