Abstract. The world's poultry industry has grown into a multibillion-dollar business, the success of which hinges on healthy intestinal tracts, which result in effective feed conversion. Enteric disease in poultry can have devastating economic effects on producers, due to high mortality rates and poor feed efficiency. Clostridia are considered to be among the most important agents of enteric disease in poultry. Diagnosis of enteric diseases produced by clostridia is usually challenging, mainly because many clostridial species can be normal inhabitants of the gut, making it difficult to determine their role in virulence. The most common clostridial enteric disease in poultry is necrotic enteritis, caused by Clostridium perfringens, which typically occurs in broiler chickens but has also been diagnosed in various avian species including turkeys, waterfowl, and ostriches. Diagnosis is based on clinical and pathological findings. Negative culture and toxin detection results may be used to rule out this disease, but isolation of C. perfringens and/or detection of its alpha toxin are of little value to confirm the disease because both are often found in the intestine of healthy birds. Ulcerative enteritis, caused by Clostridium colinum, is the other major clostridial enteric disease of poultry. Diagnosis of ulcerative enteritis is by documentation of typical pathological findings, coupled with isolation of C. colinum from the intestine of affected birds. Other clostridial enteric diseases include infections produced by Clostridium difficile, Clostridium fallax, and Clostridium baratii.