The first prototype underwent testing from 2 February 1932, leading to a large number of modifications being made, in particular the tail and engine cowling designs were considerably revised.

These had an even larger vertical tail, interplane struts of narrower chord, and no wheel spats.

The twelve production B-34s entered service with the 37 Stíhací Letka (fighter squadron) of the Czechoslovakian Air Force in September 1934.

Until the end of the First Czechoslovak Republic in March 1939, only one aircraft was lost; B-34.4 crashed and was written off in April 1937.

One, perhaps two of these were still being used for training at Tri Duby airfield (today called Sliač Airport) in August 1944.