The inverse grand-canonical Monte Carlo (IGCMC) simulation is applied to calculate the activity coefficient of the dipolar Yukawa and Stockmayer fluids. The dependence of the activity coefficient and its dipolar contribution on the number density of a fluid at the reduced temperature T = 3.0 and reduced electric dipole moment (mu*)(2) = 1.0, 3.0, and 5.0 is presented. The results are compared with predictions of: (i) the perturbation theory (PT). (ii) the free energy and virial routes of the mean spherical approximation (MSA), and (iii) Kronome-Liszi-Szalai (KLS) approach (J. Chem. Soc., Faraday Trans. 93 (1997), 3053-3059). Comparison shows that at (mu*)(2) = 5.0 the PT results are in a very good agreement with the IGCMC data. The KLS approach yields the results convergent with the simulation one for low number densities of the fluid while the MSA free energy and virial routes underestimate and overestimate the dipolar interactions, respectively. (C) 2012 Elsevier B.V. All rights reserved.