Abstract
We present results of water maser observations in a sample of YSOs. The observations were made using the Haystack 37 m antenna during a span of time of about eight months. The sample was selected to study the variability of the water maser emission in sources with far-infrared luminosity between 300 and 24×10^3L[ sun ]. Based on the observed variability, the sample can be divided into two main groups. About half of the sources show large variations in the intensity of the stronger features (more than an order of magnitude) in timespans between one and several months, while in the other sources the changes in intensity are smaller (less than a factor of 10) but on similar timescales. Finally, the variability of the observed water maser emission does not show a clear time pattern.
