It is known that during trypsinization of the skin, the epidermis is first separated from the dermis and individual keratinocytes are dissociated by disruption of the epidermal intercellular spaces. The desmosomal unit is separated at the level of the intercellular space and the split desmosomes are internalized in plasma membrane-limited vesicles; however the fate of the hemidesmosome under such conditions has not been studied. We have recently shown (Mutasim et al: J Invest Dermatol 84:47-53, 1985) that autoantibodies from the sera of patients with bullous pemphigoid bind in vitro to hemidesmosomes but not to desmosomes providing a highly specific marker for these organelles. Utilizing these autoantibodies, we studied the fate of the hemidesmosome during trypsin dissociation of epidermal basal cells derived from the skin of neonatal BALB/c mice. During trypsinization, portions of the dermal face of the plasma membrane which include hemidesmosomes formed pits which pinched off to produce vesicles that moved toward the nucleus. This was accompanied by retraction of the tonofilaments away from the cell periphery. The mechanism of this internalization process is not yet known, but may involve contractile elements of the cytoskeleton. The highly specific binding of bullous pemphigoid autoantibodies to the hemidesmosome may prove helpful in future biochemical and immunocytochemical studies of this organelle.