High speed data (HSD) over hybrid fiber coax (HFC) holds the promise of up to 1000 times the speed now obtainable with conventional modems. This technology overcomes current bandwidth hurdles unleashing a plethora of new applications and services which provide exciting new revenue opportunities for service providers. Specific requirements to achieve a successful HSD over HFC system must, however, be accounted for in both the cable data system and the HFC plant. This paper presents critical requirements for a successful implementation of HSD over HFC based on recent deployment experiences. Topics include performance, bandwidth efficiency, operational simplicity, security, economics and return plant readiness issues.