This chapter describes the technical improvements of the two-dimensional electrophoresis pattern resulting of an optimized pH range in the first dimension. Various types of pH gradients are available. Different strategies can be applied in order to select the pH ranges for the exploration of a proteome. The resulting gels are analysed for their background, resolution, sensitivity in relation with the sample complexity. As the complete dynamic range of protein expression cannot be visualized, the high loading capacity of immobilized narrow pH gradients can be used. The limitations and possible enhancements are discussed.