The photocatalytic degradation of a herbicide derivative, glyphosate [(N-phosphonomethyl) glycine] has been investigated in aqueous suspensions of titanium dioxide at different pH values. The model compound was found to degrade more efficiently under alkaline pH where little or no adsorption of glyphosate occurs on the surface of the catalyst in the dark. The main degradation route involves the cleavage of the P-C bond giving rise to sarcosine and glycine as the intermediate products formed during the photooxidation process.