Since sodium borohydride reduces aldehyde carbonyl groups, treatment of paper with this reagent should improve its long-term stability. The work described investigated the effect on both pulp on manufactured papers, following the reduction with either water washing or calcium hydroxide treatments. The latter was preferred as it increased the longevity of groundwood paper fourfield and of kraft paper by a factor of 30. Sample preparation, ageing endurance, ph and metal content, are described and the results are tabulated. References.