An oral infection model with Taenia solium whole proglottids was used to study host-parasite relationships and the mechanisms underlying resistance to infection in pigs. In addition, an attempt was made to link the parasitological findings to serological data. Groups of six piglets aged 1, 3 and 5 months were infected and slaughtered 3 months p.i. Circulating antibody and antigen levels were monitored weekly. At autopsy total cyst counts were performed. Although the detailed carcass dissection at necropsy revealed a high variation in the number of cysts, the trend was that the number of viable cysts decreased with the age at which the animals were infected. The kinetics of the antigen levels throughout the course of the infection differed markedly between the three age groups of the experimental infection model. In the younger animals, a fast increase in titres of circulating antigen was observed in most animals, reaching a plateau as early as 2 weeks p.i. Besides its faster increase, antigen levels in pigs infected at younger ages also reached higher levels than in older animals and were associated with weaker antibody responses. Results also demonstrated that a relationship exists between the number of cysts and the titre of circulating antigen. This is promising in view of the development of an assay to quantify the progress of an active T. solium infection and would be a useful tool in epidemiological studies to assess the infection burden and the risk of transmission of the disease. The use of specific antibody-detection assays combined with circulating antigen detection could improve our understanding of this relationship.