A multi-well assay plate structure (54) and assay apparatus and a method for performing chemical biochemical assays is described. The multi-well assay plate structure (54) defines a relatively shallow substantially enclosed space (71) above a plurality of wells (76), with the enclosed space (71) having an inlet (72) and an outlet (22) separate from the inlet. Fluid introduced via the inlet (72) flows into the space (71) and/or wells (76) by displacing air. Withdrawal of the fluid via the inlet (72) or outlet leaves fluid in the wells (76) allowing various tests to be performed. Various embodiments of the structure are described. The preferred arrangement embodies the structure on a transparent plastic disk which can be used with automatic fluid handling apparatus (80) and the results assessed using optical assessment apparatus (81). The apparatus can be used to perform a variety of assays but, in particular, biochemical/chemical assay, immunoassays and genetic (DNA) assays and it can be used in a laboratory for multiple sample testing or at a point-of-care, i.e. in a surgery or clinic.