Various magnesium orthophosphates were tested as catalysts for the alkylation of aniline with methanol. The solids examined had different structures and acid-base properties dependent on the particular synthetic procedure used. They were characterized as Mg-3(PO4)(2), Mg2P2O7 and NaMgPO4, mainly. Their textural properties were determined by N-2 adsorption and their acid-base properties by cyclohexylamine and phenol adsorption, respectively. The catalysts studied give the N-allcylated products only (i.e. N- methylaniline and N,N-dimethylaniline). The magnesium pyrophosphate exhibits the highest activity of all. At high reaction temperatures (above 773 K), the catalysts are strongly deactivated through coke formation; however, their catalytic activity is stable between 523 and 623 K. At 623 K, magnesium pyrophosphate is about 68% selective for alkylation to N-methylaniline with about 45% conversion. The activity of the solids studied in this reaction is related to their acid-base properties, as is their activity and selectivity in the transformation of 2-hexanol.