This paper presents a simple method to measure tissue slice thicknesses using an ohmmeter. The circuit described here is composed of a metal probe, an ohmmeter, a counter electrode, culture medium or physiological buffer, and tissue slice. The probe and the electrode are on opposite interfaces of an organotypic hippocampal slice culture. The circuit closes when the metal probe makes contact with the surface of the tissue slice. The probe position is recorded and compared to its position when it makes contact with the insert membrane on which the tissue grows, thus yielding a thickness measurement. The method does not reduce the viability of slice cultures. Thicknesses of the slice cultures were measured under a number of culturing protocols. An initial drop in thickness occurred between 0 and 4 days in culture. Thicknesses are rather constant thereafter. The type of culture medium and the initial thickness of the tissue explant influence the thickness. Slice thicknesses were compared to a known technique by using optical measurements of slice cross-sections to obtain thicknesses. In contrast to this known technique, the proposed method does not sacrifice the slice culture for measurement purposes. The proposed measurement technique described is straightforward and rapid, about 1 min per culture.