The anal gland pathology comprises cystic anal glands (so-called anal gland cyst hamartomas), anal gland carcinomas, and anal fistulas with or without carcinoma. The differential diagnosis of these conditions from other cysts and carcinomas of the anal region can be difficult. The authors have therefore compared conventional history with mucin histochemistry in normal and pathological anal glands. In contrast to normal rectal mucosa the mucus of anal glands was characterized by strong PAS-reactivity that was completely abolished after periodate borohydride saponification indicating scarcity of absence of O-acylated sialic acids in the anal gland mucus. A pattern similar to this was found in one of two tumours classified histologically as anal gland carcinomas, in four of eight colloid carcinomas arising in preexisting fistulas, and in two cases of mucoepidermoid carcinoma of the anal region. The results indicate that the method in some cases may be of value in differentiating between carcinomas arising in anal gland epithelium and in rectal mucosa. The cystic anal glands showed decreased secretion but no qualitative histochemical differences from anal glands. On the basis of the patients' histories it is suggested that the so-called anal gland cyst hamartoma at least in some cases could be an inclusion cyst of anal glands on the inflammatory basis.