Acanthoparyphium spinulosum and Cloacitrema michiganensis are parasitic trematodes of shore birds. Acanthoparyphium spinulosum was initially described as an intestinal parasite of the plover, Chadrius domincus but may also be obtained experimentally in hatchery-raised chicks. Cloacitrema michiganensis is a cloacal parasite of Actitis macularia, Catotrophorous sempalmatus inornatus, and the seagull, Larus californica. A number of histochemical studies have been concerned with the egg shell membrane, vitellaria, and reproductive systems in helminths, but no such histochemical studies have been done on .A. spinulosum and C. michiganensis. The purpose of this investigation is to identify the chemical composition of the egg shell membranes of these two parasites and the chemical composition of the other structures in their reproductive systems. Histochemical techniques for proteins, tyrosine, polyphenol oxidase, phenolic substances, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), glycolipids, acidic lipids, acidic mucosubstances, and neutral lipids were applied to whole mount adult preparations of Acanthoparyphium spinulosum and Cloacitrema michiganensis. Malachite Green for proteins was positive in the ovary, ootype, testis, vitellaria, eggs, and egg shell membrane of A. spinulosum and in the eggs and egg shell membrane of C. michiganensis. The ovary, testis, vitellaria, eggs, and egg shell membranes of both species were positive for the Millon test for tyrosine. The Catechol reaction for polyphenol oxidase was observed in the ootype, vitellaria, eggs, and egg shell membranes of both species. Fast Red Salt B was positive in the ootype, vitellaria, eggs, and egg shell membranes of both species. Methyl Green-Pyronin Y for DNA and RNA was reactive in the ovary, ootype, testis, vitellaria, and egg shell membrane in A. spinulosum and in the ovary, testis, and vitellaria of C. michiganensis.