Durability design methods should be carried out in order to obtain long service lives for the structures in chloride containing environments. In such a design, chloride diffusion must be expressed as a mathematical model. The parameters should be determined in a realistic manner and included in this model. The scatter both in the environmental exposure conditions and structural properties should be considered with a probabilistic design. The main objective of this study is the durability design of concrete structures in chloride containing environments. The transport of chlorides into concrete was modeled using Fick's second law of diffusion and a simple software based on Monte Carlo simulation was developed to consider the scatter in the environmental exposure conditions and structural properties. The effects of some important structural parameters affecting durability were investigated.