Four species of digenetic trematodes of marine fishes from Belize are studied for allometric growth:Multitestis rotundusSparks, 1954 (Lepocreadiidae),Stenopera equilataManter, 1933 (Opecoelidae),Leurodera decoraLinton, 1910 (Hemiuridae),Prosorhynchus pacificusManter, 1940 (Bucephalidae). These are compared with six other species for which allometric growth is known. Positive growth is exhibited in all species only by the hindbody, whereas the forebody, suckers, and pharynx are negative in all. The body width, post‐testicular body, and gonads are positive in some species and negative in others. At times the body proportion or organ is growing at about the same rate as the body lengt