Abstract: This invention is directed to a plastic holder assembly for loosely holding a plurality of microtiter sample tubes, which includes a tray having a plurality of holes for receiving the tubes and having opposite vertical end walls, each of which have two spaced vertically extending slots and a horizontally extending recess between the slots; a retainer releasably nestable in the tray having a corresponding plurality of holes and having opposite vertical end walls corresponding to the end walls of the tray; a U-shaped handle extending horizontally outwardly from each of the opposite retainer end walls, each handle having two legs which slide into the tray slots respectively when the retainer is nested in the tray; a tab projecting horizontally outwardly from each of the retainer end walls between each of the two legs which snap into the tray end wall recesses respectively when the retainer is nested in the tray, the retainer having an elongated slot parallel and directly adjacent each of the end walls, whereby i