Repeated irradiation of the rabbit eye with UV rays of 312 nm wavelength (UVB) evoked the appearance of active plasminogen activator of urokinase type (u-PA) in the anterior eye segment. Using histochemistry, active u-PA appeared first in the corneal epithelium followed by the corneal endothelium, inflammatory cells in the corneal stroma and the lens epithelium. With a semiquantitative fluorescent method active u-PA was also found in the tear fluid and aqueous humour. UV rays of 365 nm wavelength (UVA) under the same conditions did not cause the appearance of active u-PA in the anterior eye segment.