The cynipid Pseudeucoila bochei (Weld) has been used in ecological research for some time (JENNI, 1951; MEYER-GRASSMANN, 1967; BAKKER et al., 1967). Recently this insect has been included in the program of the ethology department of this laboratory, partly be- cause it was felt that a study of its behaviour might contribute to a solution of some ecological problems, and partly as a topic in its own right. This paper is intended as a first contribution and will deal with courtship behaviour. It will be largely descriptive since almost nothing has been published on courtship of Pseudeucoila so far. JENNI ( 1951 ) contributes only a few lines in his extensive study of this wasp, but his description seems to be incorrect on several points (see page 647). A quantitative analysis of courtship behaviour will be presented later.