In our laboratory we have developed a relatively simple method for cardiac surgery in rats. The operation is carried out through a small incision in the chest wall using inexpensive equipment. This method allows for the delivery of tissue fragments and cells from a donor rat to an intact or damaged area of ventricular myocardium of a host rat, with easy subsequent localisation of the transplanted/grafted tissue. The rats recover well after the surgery and survive for long periods of time. The technique could also be used for the direct injection of chemicals or molecular probes into the heart. In our experiments we have found that embryonic rat cardiomyocytes that have been transplanted into adult host rat ventricular myocardium using this method survive and develop characteristics typical of heart muscle, thus indicating that using this technique the host heart offers a favourable environment for the transplanted embryonic heart cells.