We analyze the spectral density of the fluctuations in the relative humidity of Zaragoza, Spain in the period 1951-1993. A similar study has already been carried out by Vattay and Harnos <1994> using data from Hungary. These authors claim that this spectrum shows a 1/fα behavior. Our results indicate a different trend, which seems to show that relative humidity at ground level is not a self-organized critical phenomenon.¿ 1997 American Geophysical Union