Long-term changes in intensity of tropical cyclones are of considerable interest because of concern that greenhouse warming may increase storm damage. The potential intensity of tropical cyclones (PI) can be calculated from thermodynamic principles given the state of the sea surface and atmosphere, and has been shown in earlier studies to give a reasonable estimate of maximum intensity for observed storms. We calculate PI using radiosonde data at 14 tropical island locations and find only small, statistically insignificant trends since 1975. In contrast with results calculated from reanalysis data, PI at most of these stations does not show a strong increase in the mid-1990s. Both reanalysis and radiosonde PI show similar interannual variability in most regions, much of which appears to be related to ENSO and other changes in SST. Between 1975 and 1980, however, while SSTs rose, PI decreased, illustrating the hazards of predicting changes in hurricane intensity from projected SST changes alone.