Proteins in cells fold via a number of intermediates. These intermediates are quite important as they guide the protein to attain its unique native conformation. To solve the immensely difficult problem of protein folding, it is necessary to characterize intermediates which will unravel the mystery of the steps involved in the proper folding of proteins. Cytochromes-c (cyts-c) have played an important role in studies of the earliest events and intermediates in protein folding. They have always been considered as model proteins for protein folding studies due to their intrinsic properties that can be measured by multiple probes. A large number of different solvent conditions have been employed to obtain equilibrium intermediates of cyts-c. These intermediates show structural heterogeneity which is mainly due to the different solvent conditions used to induce them. In this review we present results of conformational and thermodynamic characterization of equilibrium intermediates (molten globules and pre-molten globules) of the mammalian cyts-c under different solvent conditions.