The changing and expanding nature of internal contamination issues is explored in this paper. An approach to assessing and managing internal contamination issues early in a program has been developed based on a graphic model of potential contaminant sources, flow paths, and sensitive receptors. The model provides a basis for system-aticaly identifying issues, assessing risk, identifying where the knowledge base must evolve, and mitigating significant effects. Space engineering practice must evolve to deal with the new issues. Potential solutions to internal contamination problems are discussed.Failure to comprehend and act on internal contamination issues early in a program could mean that necessary characteristics are not incorporated into the hardware and software eventually causing adverse effects on crew health, habitability, and productivity, and on research, scientific instruments and hardware in the system.