A hematology test slide has the same or similar dimensions as a chemical reagent test slide and an immunoassay test slide so that it may be used with these other slides on a single clinical instrument. The hematology slide includes, in order from top to bottom, a slide housing having a top housing member, a top cover slip, a U-shaped, transfer tape spacer, a bottom cover slip, a base gasket and a base plate. The U-shaped spacer has a curved end portion which defines a sample deposit area, where a blood sample is pipetted thereon, and a pair of straight, parallel, spaced apart legs extending from the curved end portion. The legs define a read area. A blood sample deposited on the hematology slide at the sample deposit area will flow by capillary action to the read area, where optical measurements are made on the sample.