The food-grade bacterium Lactococcus lactis has been extensively investigated during the last two decades as a delivery vector for therapeutic proteins, DNA and vaccine antigens. The bacterium represents a safe, genetically tractable vector capable of producing heterologous therapeutic proteins at mucosal sites. Here we review recent work in which recombinant L. lactis strains have been exploited as agents to treat inflammatory bowel disease, allergy and cancer. We also describe the ability of L. lactis to deliver proteins with adjuvant potential, vaccines and DNA and discuss the therapeutic possibilities of this approach.