Abstract: An analytical instrument architecture provides high analytical test throughput in a compact footprint. A dilution section creates dilutions of a sample, a reaction processing section contains containers for assay reaction and measurement, and a reagent storage section supports reagent storage and supply. Transfer probes move the dilution and reagents to reaction containers. The dilution processing section includes concentric, independently driven rings of dilution containers; the reaction processing section includes concentric rings of reaction containers driven by the same mechanism for parallel processing of assays.