Abstract: This disclosure is directed to a disposal container system enabling storage of used or contaminated articles having a generally flat, strip-shaped configuration, such as diagnostic biosensors. The disposal container is removably mountable to a supply container, and has an insertion portion provided in a wall of the disposal container. The insertion portion has a contour configured externally to guide deposit of a flat, strip-shaped article through a narrow slit, the contour further configured internally to deflect any loose articles in the interior space of the disposal container away from any accidental alignment with the slit which would cause free extraction of the articles. The disposal container may be configured for engagement with a supply container, such as a round or non-round vial, in a bottom-cap configuration or in a side-by-side configuration, by way of an engagement portion.