Growth of the polyopisthocotylid monogenean Metamicrocotyla macracantha was studied in relation to the size of its host, the striped mullet Mugil cephalus. Forty-nine adult monogeneans were collected; total length, body length, haptor length, and clamp widths were measured and compared with host total length. Although no significant correlation between these size parameters of M. macracantha and that of the host was found, the haptor of the worm was found to reach a maximum length while its body continued to elongate. Such a growth pattern may be indicative of a less-efficient haptor resulting in the unique coiling behavior of M. macracantha.