Blade-like stem (10) of a hip joint prosthesis for anchoring in the femur, having a portion (19) comprising a prosthesis neck (18) on the one hand and a femur-anchoring portion (21) tapering towards a distal end (20) on the other hand, the lateral narrow side (22) of which comprises a distal straight portion (23) and a proximal arcuate portion (11), the straight portion (23) extending over a length (L.sub.D) of from 60% to 75% of the total length (L.sub.G) of the stem (10).