Crossmodulation has historically been one of the basic parameters in the specification of CATV system performance, but it is now considered by many to be an insignificant factor. However, crossmodulation continues to be an issue with CATV operators and there exists some confusion in the industry as to its measurement, and hence as to the correlation of measurements. In general, there is no industry consensus regarding its significance and acceptable levels. This paper discusses its definition and measurement, and describes tests made to correlate measured distortion with observed impairment to a TV picture. The authors concluded the visibility threshold for crossmodulation interference to be approximately -3ldB when measured in accordance with the NCTA definition.