The cresol (methylphenol) transformation on zeolite USHY was investigated in a flow reactor at 380 degreesC and atmospheric pressure. The results are compared with those previously reported for HZSM-5 (J. Catal. 172, 307 (1997)). On USHY, the catalytic stability follows the sequence p- greater than or equal to m- > o-cresol, the turnover numbers (TONs) are similar for all three cresol isomers, but slightly higher for p-cresol. Thus, the access to acid sites is not limited. While on HZSM-5, the cresol reactivity follows the sequence p- > m- > o-cresol, with the TON in the ratio p: m:o =7:4:1. The HZSM-5 zeolite catalytic activity is more stable and its acid sites are more active than those of USHY, for p- and m-, but not for o-cresol, which means that o-cresol's access to the active sites in HZSM-5 is limited. The cresols are transformed through two main routes, a unimolecular isomerization via a 1,2-methyl shift and a bimolecular disproportionation or transalkylation reaction. On HZSM-5, isomerization is the dominant pathway for all cresols, disproportionation being limited by the space available near the acid sites and by the acid site density; while on USHY, a large pore zeolite with a higher acid site density, disproportionation is more significant. On both zeolites, o-cresol shows the highest disproportionation selectivity, which could be due to a rapid formation of diphenylmethane intermediates via a benzylic carbocation of o-cresol. The plo and m/o ratios obtained for m- and p-cresol transformation respectively are higher with HZSM-5 than with USHY, while the p/m ratios obtained for o-cresol transformation were similar on both catalysts. It is concluded that not only with HZSM-5 but also with USHY the selectivity of isomerization is governed by product desorption/diffusion. The cresol composition at high conversions on USHY is 44% o-cresol, 42% m-cresol, and 14% p-cresol, which contrast with the composition found on HZSM-5: 36% o-cresol, 48% m-cresol, and 16% p-cresol. The xylenol distribution is governed by rapid interconversion and differences in diffusivities.