The main goal of this paper is to describe and discuss pathological lesions observed in a Roman skeleton (between 2nd and 3rd century AD) from the north‐east region of the Iberian Peninsula (St Nicasi 18–24 site. Gavà, Barcelona), which may be compatible with treponematosis. Most of the skeleton, with the exception of the neurocranium, was recovered. Only the left tibia was affected, whereas the rest of the recovered skeletal remains were unaffected. Macroscopic examination revealed a male individual between 25 and 30 years of age at death with a sabre‐shaped left tibia. The proximal half of the diaphysis was pitted and the bone overall enlarged. The surface of the tibia showed occasional vascular impressions where, in some instances, small raised plaques of new bone appeared to bridge over them, specifically in the most affected area of the proximal half of the tibia. No destructive lesions were observed. Radiographic examination and gross inspection at the cross section of the tibia showed encroachment into the medullary cavity of coarse cancellous bone and cancellization of the cortex. The observed lesions indicate that the tibia was affected by a chronic infectious disease. Differential diagnoses were considered, and these included other infectious diseases, fibrous dysplasia, Paget's disease, chronic varicose ulcers affecting bone and trauma, with the conclusion that the disease affecting the tibia could have been treponematosis.This could be significant in the history of the treponematoses being one of the oldest examples of treponematosis in pre‐Columbian Europe. Copyright © 2011 John Wiley & Sons, Ltd.