The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format. ; Biochemical studies have been made on liver tissue and blood from ducklings and various breeds of chickens maintained on standard rations containing 0·5 ppm of aflatoxin B₁. The results obtained from these birds were compared with those from birds of the same age maintained on groundnut-free mashes. Of the various breeds of chickens studied, only New Hampshires have been found to be susceptible to the effects of this level of aflatoxin. In the livers of affected chickens and ducklings a marked decrease in the activity of certain mitochondrial dehydrogenases and enzymes of the electron transfer chains or oxidative phosphorylation mechanisms is apparent. Mild to moderate anaemia, severe hypo-proteinaemia and grossly abnormal plasma protein electrophoretograms are presented by affected birds. It is believed that the suppression of protein synthesis observed and affecting the albumin fraction in particular, is due to a lowered rate of ATP synthesis consequent to mitochondrial injury. An increase in the activity of certain plasma enzymes, notably those of lactic dehydrogenase, aldolase and glutamic-oxalacetic- or glutamic-pyruvic transaminases, is also seen in these birds. This increase in the activity of plasma enzymes can be correlated with the severe hepatic lesions. The use of these various studies in the diagnosis of this condition, before hepatic lesions are evident, has been suggested. The ability of affected birds on rations containing 0·5 ppm of aflatoxin to recover rapidly when placed on toxin free rations is noted. Aflatoxin at these levels appears to have no cumulative effects, but no resistance is built up to its actions by tissues of birds exposed to it for long periods. Susceptible birds revealed no evidence of aflatoxicosis after prolonged feeding of dairy or poultry products obtained from cows or fowls ...