The wood anatomy of 18 genera belonging to the Lythraceae is described. The diversity in wood structure of extant Lythraceae is hypothesized to be derived from a prototype with scanty paratracheal parenchyma, heterogeneous I uniseriate and multiseriate rays, (septate) libriform fibres with minutely bordered pits, and vessels with simple perforations. These characters still prevail in a number of Lythraceae. Specialization has been very limited in most Lythraceae of shrubby or herbaceous habit: these have juvenilistic rays composed mainly of erect rays and sometimes completely lack axial parenchyma. Ray specialization towards predominantly uniseriate homogeneous rays, concomitant with fibre dimorphism leading to abundant parenchyma differentiation, and with the advent of chambered crystalliferous fibres has been traced in the “series” Ginoria, Pehria, Lawsonia, Physocalymma and Lagerstroemia. The latter genus has the most specialized wood anatomy in the family and has species with abundant parenchyma as well as species with alternating bands of dimorphous septate fibres. Pemphis represents an independent specialization with its vasicentric parenchyma and thick-walled nonseptate fibres. The affinities of Lythraceae with other Myrtales are discussed. Punica, Rhynchocalyx, Psiloxylon, Oliniaceae, Alzatea, Sonneratiaceae, Onagraceae and Melastomataceae all resemble Lythraceae in their wood anatomy. The former three genera could even be accommodated in the family without extending its wood anatomical range. Oliniaceae, Alzatea and Sonneratia only differ in minor details from Lythraceae. In order to facilitate identification of wood samples, tentative keys to the genera or groups of genera of Lythraceae as well as to some species of Lagerstroemia are presented.