The reaction cross section (σ R ) is calculated using the optical limit of the Glauber theory. A density-dependent effective nucleon-nucleon (NN) cross section σ NN is considered. Finite and zero range NN interactions are studied. The effect of finite range and an appropriate local density can increase σ R up to 20% compared to the zero range at constant density (0.16 fm −3 ), while a zero range calculation with free NN cross section increases σ R up to 13%. These factors affect the values of the rms radii for neutron rich nuclei extracted from σ R . PACS number(s): 24.10. Ht, 25.60.Dz, Recently, the optical limit to Glauber theory [1] has been used with considerable success to describe the nucleus-nucleus reaction cross section σ R [2]. The inputs to these calculations are the NN cross section σ NN and the density distribution of the interacting nuclei. The cross section σ R is usually calculated by assuming a zero range force of the interacting nucleons, and σ NN is considered through different approaches. First, σ NN is taken directly as a free NN cross section σ f NN without density dependence [3,4], and Cai Xiangzhou et al.[5] developed a density-dependent formula (in medium) averaged over the isospin of the interacting nucleiσ NN . In this approach, σ NN is usually evaluated at a constant global density ρ = 0.17 fm −3 [2,5].The method of calculating σ R is improved by using the density-dependent σ NN derived in Ref. [5]. One of these attempts [6] showed the effects of the in-medium NN cross section on σ R , using zero range NN force and the isospin averaged constant density-dependent NN cross section. Later, Warner et al. [7] introduced the local matter density in σ NN for each volume element of the nuclear overlap region; as a result the value of σ R is reduced by a relatively small percentage compared with that obtained using free NN cross section σ f NN . The effect of the finite range force [8] is found to increase σ R by about 5% compared to the zero range force for the reaction 238 U + 12 C.The main in-medium effect in the NN cross section at low and intermediate energies is due to Pauli blocking; this prevents the scattered nucleons from going into occupied states in binary collisions between the projectile and target nucleons. The accurate treatment of Pauli blocking is the geometric approach [9], which requires numerical calculation of a fivefold integral to get the in-medium NN cross section. Due to this complexity, many authors simplified the effect of Pauli blocking by making different approximations [7,[9][10][11].Although most of the recent calculations of σ R use the density dependence parametrization of Ref.[5] to include inmedium effects in σ NN , it is interesting to compare this method with the one obtained by the geometrical approach for Pauli blocking [9], when either finite or zero range NN interaction is assumed.In the optical limit of the Glauber theory, the calculation of σ R is known to be affected by the in-medium effects of σ NN , the finite range of the NN force, and the root ...