The myocardial performance was studied in 3 collagen diseases, i.e. rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and progressive systemic sclerosis (PSS). Sixteen patients with SLE, 12 with RA and 11 with PSS were examined, measuring the systolic time intervals from the first derivative of the carotid pulse in all cases. The ejection fraction (EF), was evaluated in 33 patients using radionuclide left ventricular angiography. The systolic time intervals were compared to those of 103 normal persons and the EF to that of 22 normal controls. In the SLE group the pre-ejection period was significantly shorter, while the ejection period was longer than normally expected. In the same group, the EF was significantly higher that the EF of the control group. These differences could not be related to age, blood pressure, disease duration, coronary risk factors, heart rate or blood values. Most findings in the RA group tended to be opposite to those of SLE. It is concluded that in SLE before any direct involvement of the heart the systolic time intervals and the EF present features similar to those of increased cardiac performance.