Designing modern hearing aids is a formidable challenge. The size of hearing aids is constantly decreasing, making them virtually invisible today. Still, as in all other modern electronics, more and more features are added to these devices driven by the development in modern IC technology. The demands for performance and features at very low supply voltage and power consumption constantly prove a challenge to the physical design of hearing aids and not at least the design of the ICs for these. As a result of this all large hearing aid manufacturers use fully customized ASICs in their products to produce a competitive advantage. This presentation will give a brief insight into the hearing aid market and industry, a brief view of the historic development of hearing aids and an introduction to how a modern hearing is constructed showing the amplifier as the key component in the modern hearing aid. The size of the amplifier is critical for the size of the final hearing aid and a study of the size of these for different manufactures will be presented. Designing the ICs for hearing aids poses many challenges and is a constant compromise between size, power consumption and performance of the individual blocks and some of these will be highlighted in the presentation. Finally, the future perspective for ICs for hearing aids will be discussed.