Self-diffusion coefficients have been determined by pulsed field gradient nmr methods for spermidine in solutions of the oligonucleotides d(GC)4 and d(GGAATTCC). The self-diffusion behavior of spermidine in solution of d(GC)4 is very similar to that observed previously for methylspermidine (completely N-methylated spermidine). Moreover, the self-diffusion behaviors of spermidine in solutions of d(GC)4 and d(GGAATTCC) are also quite similar, indicating that there is no significant influenceon on self-diffusion of oligonucleotide base composition. Furthermore, self-diffusion coefficients of the oligonucleotide d(GC)8 show only a small dependence on oligonucleotide concentration, and no measurable dependence on sodium ion or magnesium ion concentration.