Investigations in our laboratory showed that exposure to ultraviolet radiation significantly diminishes wound tensile strength in hairless guinea pigs. A recurring question is whether changes in wound tensile strength are reversible. The present project addresses whether wound tensile strength in irradiated and control animals differs following a 90-day healing period after irradiation and wounding. Group 1 animals (n = 10) served as nonirradiated controls. Group 2 animals (n = 10) were irradiated with a UVA/B source receiving a cumulative dose of 8,960 joules/cm2 over a 16-week period. Following completion of the irradiation schedule, a standard 6 cm midline incision was made on the dorsum of each animal and then allowed to heal for 90 days. At this time, wound tensile strength measurements were performed. The mean wound tensile strength value for the control group (4.62 +/- 0.16) was not significantly different compared to the irradiated animals (4.23 +/- 0.24). The alteration in wound tensile strength observed at 21 days in animals irradiated with a UVA/B light source is reversible after a 90-day recovery period.