The aim of the present work is to evaluate the condition of the naphtha hydrotreater furnace tubes of an oil refinery. These tubes were manufactured of SA 312 P321 material and remained in service for about twenty-five years. Two different techniques were applied for the condition assessment of used and fresh tubes - non-destructive (ND) examination and fracture mechanics based fractographic evaluation. Based on the ND testing, significant deterioration of material was noted in the used specimens. Similarly, besides micro-structural defects, the used material also exhibited sufficient loss of hardness. On the other hand, mechanical properties obtained from standard tension, impact and bend tests also exhibited the poor condition of the tubes. A comparison of the used specimens with the un-used one shows that the condition of the furnace tubes has been considerably deteriorated and its further use for the long term service cannot be considered as satisfactory.