Interannual variations in stratospheric water vapor observed by the Halogen Occultation Experiment (HALOE) over 1991-2002 are examined, together with time series of tropical tropopause temperatures observed by a network of tropical radiosonde stations. There is strong coherence between the annual cycle in tropopause temperatures and stratospheric water vapor (producing the so-called stratospheric 'tape recorder'), and the focus of this work is to determine how well interannual changes in water vapor are correlated with observed tropopause fluctuations (associated with ENSO, the QBO, and decadal trends). These observations test and constrain our understanding of water vapor entry into the stratosphere.