Abstract: The present invention relates to a hydrokinetic injector, particularly for balneotherapeutic applications. It comprises a cylindrical pipe (10) of substantially circular internal section, a first end (12) of which is equipped with means of connection to a water supply under a pressure of about 5.10.sup.5 to about 10.sup.6 Pa; a frustoconical convergent member (18) disposed towards the second end (16) of the said pipe (10) and having a venturi coefficient substantially equal to 1.25; a cylindrical expansion chamber (20) situated immediately downstream of the said frustoconical convergent member (18) and ending in an oblong rectangular window (24) forming a second constriction of the passage section, its venturi coefficient being substantially equal to 2, and a terminal horn (26) delimiting, between the said oblong rectangular window (24) and a distal opening (28), a passage of generally pyramidal shape and of continuously and adjustably variable quadrangular section.