The ultrastructure of the spermatozoa has been investigated in three common Geophilomorpha of northern France: Necrophloeophagus longicornis, Haplophilus subterraneus and Scolioplanes acuminatus. In these three genera the spermatozoa are long and thread-like. Nevertheless, specific differences are shown. The length and shape of the acrosomes vary within the species studied. The nucleus shows always two different zones: a granular zone wound in a prominent helix around a central and linear zone of fibrillar or fibrillo-granular material. The connecting organite is either round-headed or ogive-shaped. The middle piece contains the flagellar complex, eccentric and provided with a thin sheath in N. longicornis and S. acuminatus, or subaxial and surrounded by a thick sheath in H. subterraneus. In all genera studied the mitochondria have different structures according to their places along the middle piece: mitochondria are high in the anterior part and low and wide in the middle and posterior parts of the middle piece. Moreover, cavities between mitochondria are filled with particles of glycogen. The structures of the end pieces are comparable in the three species.