Born in Moscow, he studied medicine at Dorpat (now called University of Tartu), Göttingen, Berlin and Prague, but did not practise for long.

[1] Junker was a leisurely traveller and a careful observer; his main object was to study the peoples with whom he came into contact, and to collect specimens of plants and animals, and the result of his investigations in these particulars is given in his Reisen in Afrika (3 vols., Vienna, 1889–1891), a work of high merit.

[1] He investigated the Nile-Congo watershed, successfully combated Georg Schweinfurth's hydrographical theories, and established the identity of the Welle and Ubangi rivers.

The Mahdist rising prevented his return to Europe through the Sudan, as he had planned to do, in 1884, and an expedition, fitted out in 1885 by his brother in St Petersburg, failed to reach him.

As an explorer Junker is entitled to high rank, his ethnographical observations in the Niam-Niam (Azande) country being especially valuable although unsubstantiated in parts.