My talk will concern noise and cross-modulation from a few points of view. We all realize that noise and cross-modulation are the factors that ultimately limit the length of the system or the number of amplifiers that can be cascaded But, I'm not sure that everybody here knows exactly how to estimate how many of the amplifiers can be cascaded and when that limit is reached; and how to do this before the system is built and before you find it out in effect. I want to separate the problem into three parts: First, how do we specify or measure or estimate the noise and cross-modulation of a single amplifier? Then, knowing that, how do we estimate the accumulation of noise and cross-modulation along the trunk line and distribution amplifiers? And, the third question, where do we stop? How far do we let it accumulate before we say this is as far as we go, because we cannot degrade the picture any further?