Substituted 1-propiolylpiperazine compounds corresponding to formula I ##STR00001## in which X denotes N or C--R.sup.2, and n is an integer from 0 to 8, a method for producing such substituted 1-propiolylpiperazine compounds, pharmaceutical compositions containing such substituted 1-propiolylpiperazine compounds, and the use of such substituted 1-propiolylpiperazine compounds for modulating mGluR5 receptor activity or for treating or inhibiting pain and various other conditions, especially conditions at least partly mediated by the mGluR5 receptor.