The 5% electrode system is a standardized method for placing electrodes in high-resolution EEG and ERP studies. It extends the original 10–20 system, which has been widely used in clinical EEG, to a 10–5 system with 345 electrode locations. This system allows for more precise localization of electrodes, enabling better source analysis of EEG and ERP data. The 10–20 system, developed by Jasper in 1958, was the first standardized electrode placement system. It was later extended to the 10–10 system in 1985, which included 74 electrode positions. The 10–5 system further refines this by using 5% proportional distances between skull landmarks, providing a more detailed and accurate electrode placement. The 10–5 system is designed to accommodate modern EEG/ERP systems with up to 128 or 256 channels. It includes the standard locations of the 10–20 and 10–10 systems, and introduces new electrode positions at 5% intervals. This system ensures consistency in electrode placement across different laboratories, facilitating comparison of EEG data between studies. The nomenclature of the 10–5 system follows a logical extension of the 10–10 system, with new electrode positions labeled based on their location relative to existing landmarks. The 10–5 system also addresses the limitations of the 10–20 system, particularly in terms of anatomical variability. While the 10–20 system is based on fixed distances, the 10–5 system uses proportional distances, allowing for more accurate electrode placement. This system is particularly useful for source analysis of EEG data, as it provides a more detailed spatial representation of brain activity. The 10–5 system is supported by manufacturers of EEG equipment, who have developed electrode caps that facilitate the placement of electrodes according to the 10–5 system. This system is essential for high-resolution EEG and ERP studies, as it ensures standardized and reproducible electrode placement.The 5% electrode system is a standardized method for placing electrodes in high-resolution EEG and ERP studies. It extends the original 10–20 system, which has been widely used in clinical EEG, to a 10–5 system with 345 electrode locations. This system allows for more precise localization of electrodes, enabling better source analysis of EEG and ERP data. The 10–20 system, developed by Jasper in 1958, was the first standardized electrode placement system. It was later extended to the 10–10 system in 1985, which included 74 electrode positions. The 10–5 system further refines this by using 5% proportional distances between skull landmarks, providing a more detailed and accurate electrode placement. The 10–5 system is designed to accommodate modern EEG/ERP systems with up to 128 or 256 channels. It includes the standard locations of the 10–20 and 10–10 systems, and introduces new electrode positions at 5% intervals. This system ensures consistency in electrode placement across different laboratories, facilitating comparison of EEG data between studies. The nomenclature of the 10–5 system follows a logical extension of the 10–10 system, with new electrode positions labeled based on their location relative to existing landmarks. The 10–5 system also addresses the limitations of the 10–20 system, particularly in terms of anatomical variability. While the 10–20 system is based on fixed distances, the 10–5 system uses proportional distances, allowing for more accurate electrode placement. This system is particularly useful for source analysis of EEG data, as it provides a more detailed spatial representation of brain activity. The 10–5 system is supported by manufacturers of EEG equipment, who have developed electrode caps that facilitate the placement of electrodes according to the 10–5 system. This system is essential for high-resolution EEG and ERP studies, as it ensures standardized and reproducible electrode placement.