A self-contained portable sanitation unit formed in two vertically stacked sections. The top section includes a seat and cover, a bowl having an outlet port at its bottom, walls defining with the bowl a flush water chamber surrounding the bowl, and pump flush apparatus for discharging flush water into the bowl. The pump apparatus and the bowl are constructed and arranged to assure that the flush water is discharged from a discharge nozzle in a stream against the bowl wall so as to substantially eliminate "spitting" or other undesirable splashing of water thereby eliminating need for a flush rim. The lower section functions as a holding tank and is sealed from the environment by a manually actuated slide valve assembly which has its valve body and valve blade located within the holding tank to conserve vertical space, and the handle for the valve blade is located at the front of the unit. The sections are releasably secured together by a clasp mechanism located between the sections and the clasp handle is also located at the front of the unit, thereby minimizing space requirements on opposite sides of the unit. Similarly, clamp brackets for clamping the holding tank section to a support surface can be released from a frontal position and the top section alone or the two sections can be removed from a frontal position.