Antibodies to the three major components of the complex called soluble extractable nuclear antigen (ENA) were detected by passive hemagglutination (HA), counterimmunoelectrophoresis (CIE) and double immunodiffusion (DI) in 256 patients with connective tissue diseases. Anti-ENA antibodies were demonstrated by all the three employed methods in only 44.9% of the cases. These methods were not able to detect all antibodies to these antigens or any single specificity; CIE was however the most sensitive method for anti-RNP and HA for anti-Sm antibodies, while DI was the most suitable technique for serum samples with multiple anti-ENA specificities. Only in less than 50% of the cases the specificity detected by HA was comparable with that given by CIE or DI. Hence, for detecting anti-ENA antibodies a combination of these methods should be maintained, at least until more precise and reliable methods will become available.