Abstract: A tooth for a rotary drilling tool, more particularly an earth drill especially adapted for drilling in rocky soils is described including a working or cutting portion and a retaining portion; said working portion having at least one longitudinal edge provided with a rib extending up to the cutting edge of the tooth in order to receive a tungsten carbide tip, the thickness of the web portion of said working portion of the tooth being smaller than that of said ribbed edge; said web being substantially bevelled in longitudinal section, the junction between at least one face of the retaining portion of the tooth and the working portion forming a transverse rib which defines a transverse shoulder designed to cooperate with the front side of a tooth carrier of said tool.