Many of his early papers are concerned with the study of Whitehead products and their behaviour under suspension and more generally with the (unstable) homotopy groups of spheres.
This period of his work culminated in his book Composition methods in homotopy groups of spheres (1962).
Among his most important contributions to stable homotopy theory is his work on the existence and non-existence of so-called Toda–Smith complexes.
They can be used to construct the Greek letter infinite families in the stable homotopy groups of spheres.
In his paper On spectra realizing exterior parts of the Steenrod algebra (1971), Toda deduced several existence and non-existence results on these complexes.