The amino group stretching frequency (νNH) and the ¹⁵N chemical shift (δ¹⁵N) were measured for saturated primary amines. A good linear relationship was found between them, with the slope being the opposite of that found in substituted anilines. A linear relationship was also found for substituted anilines between νNH and the ¹⁵Nâ ¹H spin coupling constant (¹ J ¹⁵N,¹H). CNDO/2 calculations were done for representative molecules to obtain the NH stretching frequency, the local paramagnetic term of ¹⁵N, and the nitrogen 2sâ hydrogen 1s bond order, on the basis of which the characteristic behaviour found for the i.r. and n.m.r. parameters was interpreted.