Morphological, anatomical and ultrastructural differences between leaf tissues of field-grown and normal and hyperhydric in vitro-cultured Eucalyptus saligna were investigated. Hyperhydric material showed abnormal, often discontinuous development of the epidermis and cuticle. Stomata were malformed. The leaf lamina appeared thickened and was characterized by poor differentiation between the palisade and spongy mesophyll. The chlorophyll content of hyperhydric material was significantly less than that of field-grown and normal cultured material. Hyperhydric leaves had a significantly lower chloroplast number per cell and chloroplasts showed reduced thylakoid stacking. The gross photosynthetic rate of hyperhydric tissue was less than that of normal cultured material.