MCP-1 is a small (8-10 KDa) protein and a prototype member of the CC chemokine beta subfamily, which plays a critical role in acute and chronic inflammation. Recent evidence suggests an important role for MCP- 1, MCP-2 and MCP-3 in a number of pathological states, including delayed type hypersensitivity conditions, parasitic infections and rheumatoid arthritis. Forty BALB-c mice were treated with the parasite Trichinella spiralis. After the infection the animals were sacrificed at different periods from the initial infection and MCP-1 and TNFalpha were quantified in the mouse serum. The level of MCP-1 in the serum of mice infected with 100 larvae increases from 27.5+/-7.0 pg/ml at day 23, to a maximum level of 31.5+/-5.0 pg/ml at day 33, then decreased to 14.6+/-2.0 pg/ml at day 47. When the mice were infected with 200 larvae of T. spiralis the maximum increase was 34.4+/-2.5 pg/ml found on day 23. From day 33 to day 47 MCP-1 levels were decreased. In addition, in infected mice levels of TNFalpha were detectable in the serum as early as day 1. The level of TNFalpha was maximum at day 35 (3812+/-224 pg/ml). Serum from non-infected mice contained no detectable levels of either MCP-1 or TNFalpha. However, even if MCP-1 seems to be implicated in Trichinellosis, its exact role and function in inflammatory parasitic diseases remains to be determined.