Injection-moulded bars made from polypropylene, polystyrene and polycarbonate have been tested in tension at slow strain rate (mainly 1.1-1.4 x 10(-7)s(-1)). in some cases, the bars were exposed to ultraviolet irradiation (UV) simultaneously. Notched bars were used and were found to fail earlier when exposed to UV. The maximum load attained in the slow strain-rate test was found to be a suitable characteristic to represent the extent of the degradation caused by UV exposure. Pre-exposure to UV caused further reduction in performance during the slow strain-rate test. Of the materials tested, polycarbonate was least affected by UV exposure.