The hydrophilic metabolome of tall fescue (Festuca arundinacea) adapted to grow in naphthalene-treated sand (0.8 g kg(-1) sand dw) was analysed using gas chromatography-mass spectrometry, and peaks corresponding to the more abundant compounds were tentatively identified from analysis of their mass spectral features and reference to the NIST Mass Spectral Database. Particular attention was paid to sugars as they are known to play important roles as stress regulators in plants. The results showed that the abundance of sugars was greater in the roots but lesser in the shoots of treated plants when compared to their control counterparts. The results for indole acetic acid (IAA) were notable: IAA was prominently less in the treated roots compared to shoots, and in treated shoots, IAA was particularly subdued compared to untreated shoots consistent with IAA degradation in treated plant tissues. The differences in the molecular phenotype between control and treated plants were expressed in root structural differences. The treated roots were modified to have greater suberisation, enhanced thickening in the endodermis and distortions in the cortical zone as demonstrated through scanning electron and epi-fluorescence microscopy.