T wave morphology is important in diagnosing conditions such as myocardial infarction and hyperkalemia. The T wave should be evaluated by its morphology, amplitude and polarity. Morphologically it is assymetric, with the first half having a more gradual slope than the terminal portion. T wave amplitude is variable, but the T waves are tallest in the mid-precordial leads, usually V2 and V3. T wave polarity generally follows QRS polarity. In the frontal leads, The T wave should always be positive in lead I and II, and negative in lead aVR. It might be positive or negative in lead III, aVF and aVL. In the precordial leads, the T wave may be positive or negative in V1, and rarely in V2, but always positive in V3-V6. Beginning from the right precordial leads, once a T wave is positive it should remain positive as it progresses towards the left.