Black liquiors from kraft pulping and as well as a purified kraft lignin were reacted with formaldehyde over the temperature range 30-70C. The activation energy was about 12.9 Kcal per mole. They were also heat treated to "activate" the lignin and some were also reacted with formaldehyde or furfuraldehyde. These treated solutions were then mixed with phenolformaldehyde (PF) resols and used as plywood adhesives. They were first used in suspension at pH 5.3-5.5 with an acid-curing PF resin. This method proved unsatisfactory. When used as solutions mixed with polymethylophenol resols at solids content varying from 40 to 60 per cent of total solids (resol solids plus black liquor solids) and pH about 12.0, good bonding was obtained with either crude or methylolated black liquor or kraft lignin solutions on 3/8 inch (9.6mm) aspen poplar plywood pressed at 350F (177C) fro 5 minutes and 150 per square inch (1034 kPa). Phenolic resin requirements were 40 to 56.5 percent of the amount required when pure PF is used.