Experiments were carried out to assess the effects of feed-borne ' Fusarium' mycotoxins with or without the presence of coccidian challenge on the metabolism and performance of broiler chickens and turkey poults. The efficacy of a polymeric glucomannan mycotoxin adsorbent (GMA) in preventing or reducing the adverse effects of mycotoxins was also evaluated. These experiments demonstrated that feeding grains naturally contaminated with 'Fusarium ' mycotoxins can severely reduce ('P'<=0.05) growth performance, and affect plasma biochemistry and hematology, immunoglobulins and intestinal histological parameters in broiler chickens and young turkey poults. The supplementation of GMA to a mycotoxin-contaminated diet (' P'<=0.05) prevented some of these adverse effects. The co-occurrence of both mycotoxin and coccidian infection (' P'<=0.05) increased the severity of challenge on the birds which was most evident in growth performance and intestinal morphometric parameters. Interactions in these experiments ranged from synergistic to antagonistic. At times additive or less than additive interactions was observed. It was concluded that feeding grains contaminated with 'Fusarium' mycotoxins can have severe consequences on birds' performance and can be exacerbated by the presence of coccidiosis.