Previous electron spin resonance studies in myotonic muscular dystrophy (MyMD) have suggested that an increased cell surface membrane "fluidity" might underlie the widespread abnormalities in this disorder. We attempted to confirm and expand those findings by using another physical probe technique: fluorescence polarization spectroscopy. Spectral characteristics and rotational relaxation rates of four hydrophobic fluorescent probes were monitored in control and MyMD erythrocyte membrane ghosts. Structural unrelated probes were used to minimize the possibility that an alteration in physical properties in a restricted membrane microdomain would pass undetected. All probes were studied between 5 degrees C and 40 degrees C in each preparation to quantitate temperature-dependent changes. We failed to confirm the abnormality in apparent membrane fluidity previously reported in MyMD.