Abstract: An analytical device for determining the presence and/or concentration of an analyte in a sample liquid comprises a hollow casing; an assay strip within said casing for selectively capturing an analyte in sample liquid applied to the device; a bibulous sample liquid receiving member at or adjacent to a first extremity of said casing which collects sample liquid and transports it into the casing; a window in the casing at a location remote from the first extremity of the casing; and a single cap which can be applied in turn over the window during sample collection, and then over the sample receiving member.