We present high-accuracy simulation data for ion-ion radial distribution functions in NaCl aqueous electrolyte. From the data we evaluate ion-ion effective potentials via inverse Monte Carlo simulation procedure. Alternatively, we first evaluate effective direct correlation functions and then obtain effective potentials using the hypernetted-chain (HNC) approximation. Both methods are in excellent agreement, indicating that HNC approximation performs well with effective ion-ion potentials in aqueous solutions.