(Principal source: Koerner 1983) Pedersen studied at the University of Copenhagen with Karl Verner, Vilhelm Thomsen, and Hermann Möller.

He subsequently studied at the University of Leipzig with Karl Brugmann, Eduard Sievers, Ernst Windisch, and August Leskien.

His Hittitisch und die anderen indoeuropäischen Sprachen, 'Hittite and the Other Indo-European Languages', represented a significant step forward in Hittite studies, and is often relied on in Friedrich's Hethitisches Elementarbuch (2d ed.

Also influential was his Tocharisch vom Gesichtspunkt der indoeuropäischen Sprachvergleichung, 'Tocharian from the Viewpoint of Indo-European Language Comparison'.

It was Pedersen who formulated the ruki law, an important sound change in Indo-Iranian, Baltic, and Slavic.

In his classic exposition of the theory, Émile Benveniste (1935:148) credits Pedersen as one of those who contributed most to its development, along with Ferdinand de Saussure, Hermann Möller, and Albert Cuny.

Pedersen therefore proposed that the three stop series of Indo-European, p t k, bh dh gh, and b d g, had at an earlier time been b d g, ph th kh, and (p) t k, with the voiceless and voiced non-aspirates reversed.

Under this form, the theory has attracted wide interest; however, since the original claim of typological oddity has been falsified, no direct evidence for glottalized stops has been found,[1] in the last few years publications in support of the so-called glottalic model have been steadily declining, and "the traditional paradigm remains absolutely in place".

English "Nostratic" is the normal equivalent of German nostratisch, the form used by Pedersen in 1903, and Danish nostratisk (compare French nostratique).

In his 1924 book, Pedersen defined Nostratic as follows (1931:338): In his view, Indo-European was most clearly related to Uralic, with "similar, though fainter, resemblances" to Turkish, Mongolian, and Manchu; to Yukaghir; and to Eskimo (1931:338).

In modern terms, we would say he was positing genetic relationship between Indo-European and the Uralic, Altaic, Yukaghir, Eskimo, and Afro-Asiatic language families.