Using three different methods evidence was obtained that native and deglycosylated choriogonadotropin show differences in their conformations which might account for the antagonistic properties of deglycosylated choriogonadotropin: 1. In the deglycosylated hormone additional peptide bonds were susceptible to chymotrypsin. 2. In the far ultraviolet circular dichroism only small differences existed between native and deglycosylated choriogonadotropin. However, in 80% hexafluoropropanol the deglycosylated hormone adopted a higher degree of ordered structure. 3. At 37 degrees C the deglycosylated hormone showed a 13 fold increase of the dissociation rate into subunits at pH 3 in comparison to native choriogonadotropin. The results provide evidence that in chemically deglycosylated choriogonadotropin the subunit interactions are disturbed due to conformational changes.