In this paper we investigate (using AMI semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-31G^* and 6-31G^** level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate from of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation effects, are correlated with recent experimental results.