The invention relates to hexahydro-pyrido[1,2-a]pyrazine derivatives having interesting neurokinin-NK.sub.1 receptor antagonistic activity. The invention also relates to methods for the preparation of these compounds, to pharmaceutical compositions containing a pharmacologically active amount of at least one of these compounds as an active ingredient, as well as to the use of these compositions for the treatment of disorders in which neurokinin receptors are involved. The invention relates to compounds represented by the general formula (1) ##STR00001## wherein the symbols have the meanings as given in the description.