The intestinal mucosa is reported to be greatly affected by infestation by Trichinella spiralis. The infestation by the worm is also controlled by intestinal tissue factors including cytokines and immune response. Vaccination with larval muscle antigen was reported to be of limited effect. However, vaccination with adult worm crude antigen may infer better protection. The aim of this work is to relate the histological, morphometric and immunological response of the intestinal mucosa of T.spiralis infested rat to worm burden, female fecundity and worm expulsion before and after immunization with crude antigen of the adult worm. This relationship is expected to give better evaluation of immunization by this antigen. 45 adult albino rats were allotted among three equal groups: control, T.spiralis infested and immunized infested group. Infection was done by 300 freshly isolated infective T.spiralis larvae. Five rats from each group were sacrificed at the end of the first, second and third week of infestation. The efficacy of immunization was assessed weekly by measuring adult worm burden and female fecundity, in relation to changes in the histological appearance, relative villus length, number of goblet, and mast cells and the amount of histamine in the intestine. The results indicated that the worm burden was at its peak by the end of the first week after infestation. The mean protection value due to immunization in this parameter was 67%. Immunization resulted in a protection value relative to larval emergence of 38%. Maximum changes in the host tissue parameters were detected a week after that of worm burden. Measurement of the host intestinal response represented 78% change in villus/crypt ratio, 13.3% in number of goblet cells in the villus and 16.22 in the crypts, 22.5% in mast cell number and 16.8% in histamine content. The results indicate that immunization by crude antigen of the adult T.spiralis has a protective effect of the intestinal mucosa of the host due to inhibition of worm vitality and larval emergence. Mast cell production of histamine and goblet cell secretion of mucins could also play a role in protection.