A binding assay device includes a porous membrane comprising a material enabling capillary movement of a liquid sample from a first area on the membrane on a second area on the membrane. A detection site is disposed on the membrane between the first and second areas in a non-absorbent medium disposed on the membrane between the detection site and the membrane first area is attached by an adhesion with a dry reagent disposed between the medium and the membrane in order to enable mobilization of the reagent by passage of a liquid sample therepast.