A series of 1-, 3-, 5- and 6-substituted 2(1H)-pyrazinone 4-oxides were synthesized and tested for anticoccidial activity. Of the compounds tested, 1-(β-D-ribofuranosyl)-(22), 1-(2, 3, 5-tri-O-benzoyl-β-D-ribofuranosyl)-(21) and 1-(2, 3, 5-tri-O-acetyl-β-D-ribofuranosyl)-2(1H)-pyrazinone 4-oxides (24) showed high activity.