The use of proficiency tests (PTs) in an analytical inorganics laboratory is an essential part of assuring clients the laboratory is producing accurate results. In the first part of this two-part series, we examined the ways in which contaminants can alter the results in a detrimental fashion in regard to proficiency testing and laboratory audits. In Part II, we examine the actual planning, running, and reporting of a PT scheme and the possible impact of error and contamination.