This paper investigates the “in-home” environment when implementing cable modem systems in two-way HFC networks. Cable modems are hitting the market on a wide scale in 1998, with standardized performance and interfaces per the recently developed MCNS (Multimedia Cable Network System) consortium. Their ability to coexist with the existing downstream infrastructure is crucial to their acceptance as a broadband access tool. However, the modem may be required to operate at high transmit levels, potentially interfering with the downstream TV and/or settop converter unit. Also, the downstream receive equipment may introduce ingress into the return path, which can impair digital communications. Suggestions that address these serious issues are discussed. Measurement results are presented that justify these conclusions.