Balb/cJ mice infected in the peritoneal cavity with larval Taenia crassiceps fail to mount a protective immune response. In mice, inflammatory immune responses are believed to control larval reproduction, whereas antibody-mediated responses are believed to be permissive. In the present study, mice were treated with CpG-oligodeoxynucleotides (CpG) to determine whether stimulation of the innate inflammatory response would confer increased resistance to larval growth. Female mice treated with CpG displayed a decrease in mean parasite burden by 54%, while male mice displayed a 73% reduction. Moreover, 5 of 12 CpG-treated male mice completely eliminated all larvae by 9 wk post-infection. In contrast, no female animals were found to be infection free. CpG treatment induced an increase in the transcript levels of tumor necrosis factor-α and inducible nitric oxide synthase (iNOS) from splenocytes and resulted in elevated levels of the proinflammatory molecules monocyte chemotactic protein (MCP)-1, MCP-3, and interleukin-6 at the site of infection. Additionally, CpG administration induced the enhanced recruitment of neutrophils and macrophages to the site of infection. The finding that both neutrophils and macrophages were recruited in significantly higher numbers in the male host as compared to the female host may explain the increased level of protection realized in male animals in response to CpG treatment.