Abstract: Substituted phenylacetylenes of the formula ##STR1## wherein one of the groups R.sub.1 is a hydrogen atom and the other represents the group of the formula ##STR2## in which R.sub.3 is hydrogen, methyl or ethyl and R.sub.4 is a methyl or an amino group and wherein R.sub.2 represents mono- or binuclear aromatic or heterocyclic residues containing sulfur, nitrogen or oxygen as hetero atoms and optionally being substituted by 1 to 3 substituents as defined, which specifically inhibit 5-lipoxygenase and are useful in pharmaceutical compositions for prophylaxis and treatment of diseases due to the action of leukotrienes.The compounds may be prepared by reacting a compound of the formula ##STR3## wherein R.sub.2 has the same meaning as above and one of the groups R.sub.7 is a hydrogen atom and the other represents the group of the formula --COR.sub.3, with hydroxylamine to form the oxime which then is reduced to the corresponding hydroxylamine compound into which the group of the formula --COR.sub.4 is introduced.