Although mitochondria are known to move actively in plant cells, little is known about how they move. In higher plants, actin filaments have been reported to be involved in the movement of organelles, such as chloroplasts, peroxisomes, endoplasmic reticulum and Golgi apparatus. Mitochondria were visualized in living Arabidopsis thaliana plants using fluorescent proteins fused to a mitochondria targeting signal. To compare the movement of mitochondria to the movements of another organelle, we also examined peroxisomes because of their similarity in size. Velocities of individual mitochondria and peroxisomes, as measured by time-lapse laser scanning microscopy, varied, although the average velocities of the two organelles were similar. Latrunculin B, an actin-depolymerizing drug, stopped movement of mitochondria and peroxisomes, demonstrating that movement of these organelles depends on actin filaments. On the other hand, propyzamide, a microtubule-depolymerizing drug, did not affect the movement of mitochondria and peroxisomes. In living Arabidopsis plants in which mitochondria or peroxisomes are visualized by red fluorescent protein and cytoskeletal elements are simultaneously visualized by green fluorescent protein, both organelles moved using actin filaments as rails. In contrast, their movement was not related to arrays of microtubules. We also examined mitochondrial movement in tobacco cultured cells visualizing mitochondria and cytoskeletal element simultaneously. Mitochondrial movement was often seen along actin filaments but not along microtubules. These findings suggest that mitochondria move along actin filaments rapidly and over long distances in higher plants.