An immediate advance of two-dimensional gel electrophoresis (2-DE) with immobilized pH gradients is the practical solution of setting up very narrow pH gradients in the most regions of pH scale, with the resultant dramatic improvement in resolution for some applications. However, when less soluble proteins are analyzed by this technique, guantitative protein losses are observed. It was shown that protein solubility could be improved by varying the detergents and chaotropes used for rehydration of the mobile strips. A high effectiveness of a modified urea/thiourea/sulfobetaines rehydration buffer in the solubilization of proteins occurring, especially, in acidic area of 2-DE gels in which the presence of cytoskeletal proteins can be anticipated. It was also found that proteins requiring a higher amount of chaotropic substances to enter immobiline strips could be detected using a standard rehydration solution and they are lost when the urea concentration is diminished.