The activity of 2-amino-7-phosphonoheptanoic acid (2-APH), an antagonist of the NMDA subtype of glutamate receptor, was tested in several animal models of anxiolytic activity in rats and mice and compared with the activity of the standard benzodiazepine anxiolytic, diazepam. 2-APH was effective, but about 100 times less potent than diazepam in antagonising the suppressive effects of punishment on locomotor activity in the four-plate test in mice. 2-APH was also effective in enhancing exploration of the open, exposed arms of a plus maze, without altering exploration of the enclosed arms. Again 2-APH was about 100 times less effective than diazepam. In contrast to diazepam, 2-APH was ineffective in antagonising the pro-punishment properties of the anxiogenic beta-carboline DMCM in a modified four-plate test, and in antagonising the discriminative stimulus provided by pentylenetetrazol. These results are discussed in the context of the equivalence of the antagonism of excitatory mechanisms and the enhancement of inhibitory systems as anxiolytic treatments.