A quantitative treatment of ${pi}$-nonbonded and $n-{sigma}^{ast}$ interactions and through-bond coupling effect was attempted using n-butane, n-butyl radical, and tetramethylene diradical. Results of STO-3G level calculations showed that: (1) conformational preferences can be predicted quantitatively based solely on the additive effect of ${pi}$-nonbonded and $n-{sigma}^{ast}$ interactions, the predominant effect being the ${pi}$-nonbonded interactions, (2) $(n-{sigma}^{ast})_{anti}$ is destabilizing whereas $(n-{sigma}^{ast})_{syn}$ is weakly stabilizing, which are contrary to what we expect from the normal $n-{sigma}^{ast}$ interaction, (3) througb-bond coupling of the two radical lobes is destabilizing for the triplet but stabilizing for the singlet tetramethylene diradical.