This paper reviews the use of dry and noncontact biopotential electrodes for clinical applications. Traditional wet Ag/AgCl electrodes are widely used but are cumbersome and irritating for mobile use. Dry and noncontact electrodes, which do not require gels or adhesives, have been known for decades but have not been widely accepted for medical use. The paper explores the electrical models for dry, insulated, and noncontact electrodes, showing their performance limits and measured data. It demonstrates that minimizing electrode resistance may not always be necessary and can actually increase noise due to coupling capacitance. The paper reviews the latest developments in dry electrode technology and highlights novel systems enabled by dry electrode technology for cardiac and neural monitoring. It also discusses current challenges and a roadmap for future developments. The paper emphasizes that while dry and noncontact electrodes offer advantages in comfort and usability, they face challenges in signal quality and motion artifact reduction. The paper concludes that while dry and noncontact electrodes have potential for clinical applications, they are unlikely to replace traditional wet electrodes in the near future. The paper also discusses the importance of understanding the skin-electrode interface and the role of coupling conductance in noise performance and sensitivity. The paper provides a detailed analysis of the electrical model for dry and noncontact electrodes and their performance in clinical settings. It also discusses the challenges of motion artifacts and the need for mechanical solutions to secure electrodes in the proper position. The paper concludes that while dry and noncontact electrodes have potential for clinical applications, they require further development to overcome challenges in signal quality and motion artifact reduction.This paper reviews the use of dry and noncontact biopotential electrodes for clinical applications. Traditional wet Ag/AgCl electrodes are widely used but are cumbersome and irritating for mobile use. Dry and noncontact electrodes, which do not require gels or adhesives, have been known for decades but have not been widely accepted for medical use. The paper explores the electrical models for dry, insulated, and noncontact electrodes, showing their performance limits and measured data. It demonstrates that minimizing electrode resistance may not always be necessary and can actually increase noise due to coupling capacitance. The paper reviews the latest developments in dry electrode technology and highlights novel systems enabled by dry electrode technology for cardiac and neural monitoring. It also discusses current challenges and a roadmap for future developments. The paper emphasizes that while dry and noncontact electrodes offer advantages in comfort and usability, they face challenges in signal quality and motion artifact reduction. The paper concludes that while dry and noncontact electrodes have potential for clinical applications, they are unlikely to replace traditional wet electrodes in the near future. The paper also discusses the importance of understanding the skin-electrode interface and the role of coupling conductance in noise performance and sensitivity. The paper provides a detailed analysis of the electrical model for dry and noncontact electrodes and their performance in clinical settings. It also discusses the challenges of motion artifacts and the need for mechanical solutions to secure electrodes in the proper position. The paper concludes that while dry and noncontact electrodes have potential for clinical applications, they require further development to overcome challenges in signal quality and motion artifact reduction.