Spermatozoa of a commercial Australian abalone,Haliotis laevigataDonovan, 1808 (the ‘greenlip’ abalone) are examined for the first time using transmission electron microscopy. As is characteristic of other externally fertilizing molluscs, the spermatozoa ofH. laevigataare of the structurally simple type (classic ect-aquasperm). In anterior- posterior sequence, each spermatozoon consists of a conical acrosomal vesicle (length 1.35–1.38 μm, deeply invaginated posteriorly and associated with a subacrosomal axial rod and flocculent deposits), a barrel-shaped nucleus (length 2.1–2.2 μm, with prominent lacunae), a short midpiece (consisting of a pair of orthogonally arranged, triplet substructure centrioles surrounded by a five spherical mitochondria), nine satellite fibres (connecting the distal centriole to the plasma membrane) and a 40–44 μm long flagellum (featuring a 9 + 2 microtubular pattern axoneme). Total length of spermatozoa ranges from 44–48 μm. The contents of the acrosomal vesicle can be divided into anterior and posterior portions based on differing electron densities and the occurrence anteriorly of a thin, ‘truncated cone’ structure at the periphery of the vesicle. Preliminary examination of spermiogenic stages indicates that like other vetigastropods the acrosomal vesicle ofH. laevigatadevelops through coalescence of several moderately large, electron-dense, pro-acrosomal vesicles. Comparison with other species ofHaliotiswhich have been studied reveals that spermalozoa ofH. laevigata(type of subgenusSchismotis) most closely resemble those of the Asian speciesH. japonica aquatilisandH. diversicolor supertexta(members of subgenusSulculus). Such spermatozoa differ from those of other investigated haliotids (H. discus, H. mfescensof subgenusNordotisandH. midaeof subgenusEuhaliotis) all of which have appreciably longer acrosomal and nuclear regions. The use of sperm ultrastructure for probing species relationships within the Haliotidae appears to be a most promising area for future research, particularly when directed at type species of nominal subgeneric units.