Stream catchment areas digitized from existing regional stream sediment sample locations are assessed for quality and confidence of sample site location, catchment surface area (used as a proxy for downstream dilution), surface material type, slope angle and slope aspect. Rankings for each of these attributes are combined into quality indices to give an overall impression of reliability for each catchment that can be incorporated into mineral exploration targeting criteria and design of further sampling programs. Data from quality control samples included with each sample batch during a recent re-analysis program are also assessed for some key elements. Standard reference materials included in two separate re-analysis campaigns show slight shifts in bias even though the same analytical method was used in both instances. Some elements, particularly Au, show an unacceptable amount of scatter in repeat analyses of the standard reference materials indicative of a non-homogenous distribution of Au in the materials for the small sample mass (0.5 g) used for analysis. Data precision is assessed using field and blind duplicate analyses for selected elements. The Au analyses show the poorest precisions, with data from Cu giving the best precision and data for As yielding intermediate precisions.