The aim of this prospective study was to assess whether the fibrous thickening of the carpal tunnel tenosynovium is influenced by working practices. We did this by investigating 50 men (58 hands) with idiopathic carpal tunnel syndrome, who were undergoing carpal tunnel decompression. Occupational history, including vibration tool exposure, and presence of callosities and/or ingrained dirt on hands was recorded at the time of surgery. The flexor tenosynovium was biopsied, and assessed histologically by an observer blinded to occupational history. Occupational group, age, weight and smoking showed no significant association with fibrous tenosynovial thickening. There was also no significant association between fibrous tenosynovial thickening and the presence of hand callosities/in-grained dirt or regular use of vibration tools. Thus no association was found between heavy occupational hand usage and the development of fibrous tenosynovial thickening around tendons within the carpal tunnel.