The oxidation reactions of the three isomeric pyridinecarboxylic acid hydrazides were studied using sodium metaperidoate, silver(I) oxide and potassium ferricyanide separately Potassium ferricyanide emerged as an excellent reagent for preparation of 2-pyridinecarboxaldehyde and 3-pyridinecarboxaldehyde from the respective isomeric pyridinecarboxylic acid hydrazides. Oxidation with silver(I) oxide in each case yielded the corresponding 1,2-dipyridoylhydrazine, while sodium metaperiodate furnished different products with each isomeric pyridinecarboxylic acid hydrazide.