This overview summarizes important aspects of the cantilever stress measurement technique and its application to measurements of adsorbate-induced surface stress changes and magnetization-induced magnetoelastic stress (also called magnetostrictive stress) of ferromagnetic monolayers. The application of the cantilever technique as a torque magnetometer with monolayer sensitivity is demonstrated. The stress measurements indicate a correlation between surface stress changes and surface reconstruction, and they also identify the often decisive role of the magnetoelastic anisotropy for the non-bulklike magnetic anisotropy of ferromagnetic monolayers.