  We present the analysis of photometric and spectroscopic data of two bright
Galactic Cepheids, X Puppis and XX Sagittarii. Based on the available data in
the literature as well as own observations spanning 75 years, we conclude that
both Cepheids belong to spectroscopic binary systems. However, the data are not
sufficient to determine the orbital periods nor other elements for the orbit.
This discovery corroborates the statement on the high frequency of occurrence
of binaries among the classical Cepheids, a fact to be taken into account when
calibrating the period-luminosity relationship for Cepheids. The photometric
data revealed that the pulsation period of X Pup is continuously increasing
with Delta P=0.007559 d/century likely caused by stellar evolution. The
pulsation period of XX Sgr turned out to be very stable in the last ~100 years.
