We have examined four models of experimental cardiac hypertrophy and heart failure for alterations in troponin isoform expression, particularly in the re-expression of the fetal isoforms. Cardiac protein extracts from experimental and sham-operated control rats were analyzed using one dimensional gel electrophoresis, followed by Western blotting and detection with antibodies specific for troponin I and T. No alteration in protein profile was observed for these proteins between control, hypertrophied and failing heart samples. The data demonstrate that reversion to the fetal pattern of troponin expression is not a feature of experimental cardiac hypertrophy and heart failure in the rat.