Studies were performed on 149 patients, aged 18 to 50, hospitalized in the Department of Parasitic and Tropical Diseases, Medical Academy in Poznań. The following examinations were performed: gastric contents testing with histamine stimulus according to Kay, the histological and cytological examination of gastric mucosa biopsies. Among patients with Taenia saginata invasion, disturbances in secretory activity of gastric mucosa were demonstrated in 57.7% of studied patients. Hypoacidity was found in 49.7% of patients; it appeared both in the oldest group, over 40 years (71.4%), as well as in two younger, although at two times lower frequency (38.2 and 39.6%, respectively). At set of histological and cytological studies was performed on gastric mucosa biopsies in a chosen group of 30 patients (average age of 26.2 years) with taeniasis and hypoacidity, before and after the treatment of the invasion. Before the treatment cellular infiltrates consisting of mononuclear cells were observed in gastric mucosa biopsies; cytological analysis of gastric gland cross-secti-ons demonstrated 3 to 4 times lower number of parietal cells as compared to that of mucous cells. After the treatment of taeniasis, secretory activity of gastric mucosa returned to the normal level in 20 patients (66.7% of total). At the same time, the histological and cytological analysis of the biopsies showed decreased intensity of cell infiltrates in the glandular layer of the mucosa and an increased number of parietal cells as compared to the number of mucous cells. In 10 patients (33.3% of total), hypoacidity of the gastric juice as well as gastric mucosa lesions persisted despite the elimination of T. saginata. No relation could be found between the duration of T. saginata invasion on the one hand and secretory disturbances on the other. The subsidance of functional disturbances in gastric mucosa and of their morphological exponents in 2/3 of patients after taeniasis treatment indicates a causal relationship between time of taeniasis and secretory disturbances and histological lesions in gastric mucosa.