Some considerations on interharmonic voltages limits and their assessment are developed. Reference is made to recent activities in the standard review process and to research literature regarding this specific topic and related issues. Some recalls on the main interharmonic voltages effects are reported. Then, the problems related to the combined use of limits and assessment procedures based on IEC flickermeter and on DFT spectral analysis together with the sub-group concept are discussed. Finally, experimental results obtained during laboratory tests and field campaigns of measurements are reported.