Salt (NaCl) penetration was studied on dry-cured hams of different weight processed by two different salting processes. Chemical composition and water activity (a(w)) were analysed on two of the most representative ham muscles during the process. The normalized Weibull cumulative distribution was used to fit salt uptake in Biceps femoris m. (BF) and to calculate the salt diffusion coefficient. The a(w) values strictly depend on the Salt Index (S.I., g(Nacl) 100 g(W)(-1)). The S.I. of BF samples from hams taken at different processing steps, were modelled as a function of aw by both a linear and a first order polynomial model achieving good fitting (R-2 = 0.92). The calibration root mean square error (RMSE) resulted being of 1% for both models. Cross validation was performed and the RMSEs were of 0.62% and 0.61% for the linear and polynomial models, respectively. These models can be useful to manage the salting process in dry-cured hams at industrial level. (C) 2016 Elsevier Ltd. All rights reserved.