Pigs infected withAscaris suumor controls were given 100 μg (low-dose) or 1,000 μg (high-dose) all-transretinoic acid (ATRA)/kg body weight in corn oil or corn oil alone per os on days after inoculation (DAI) −1, +1, and +3 with infective eggs. Treatment with ATRA increased interleukin 4 (IL4) and IL12p70 in plasma of infected pigs at 7 DAI and augmented bronchoalveolar lavage (BAL) eosinophilia observed at 7 and 14 DAI. To explore potential molecular mechanisms underlying these observations, a quantitative real-time reverse transcription (RT)-PCR array was used to examine mRNA expression in tissue.Ascaris-infected pigs had increased levels of liver mRNA for T-helper-2 (Th2)-associated cytokines, mast cell markers, and T regulatory (Treg) cells, while infected pigs given ATRA had higherIL4,IL13,CCL11,CCL26,CCL17,CCL22, andTPSB1expression. Gene expression for Th1-associated markers (IFNG,IL12B, andTBX21), the CXCR3 ligand (CXCL9),IL1B, and the putative Treg markerTNFRSF18was also increased. Expression ofIL4,IL13,IL1B,IL6,CCL11, andCCL26was increased in the lungs of infected pigs treated with ATRA. To determine a putative cellular source of eosinophil chemoattractants, alveolar macrophages were treated with IL4 and/or ATRA in vitro. IL4 inducedCCL11,CCL17,CCL22, andCCL26mRNA, and ATRA increased the basal and IL4-stimulated expression ofCCL17andCCL22. Thus, ATRA augments a diverse Th1-, Th2-, Treg-, and inflammation-associated response in swine infected withA. suum, and the increased BAL eosinophilia may be related to enhanced induction of eosinophil chemokine activity by alveolar macrophages.