Abstract <p>The electrohydrodynamic instability of the charged liquid surface manifests itself in the instability of a highly charged drop, the instability of a charged drop in superposition of external electrostatic field and gravitational field, and the instability of flat charged surface of electroconductive liquid. Attempts to experimentally verify the correctness of the criterion of electrohydrodynamic instability of a highly charged drop, the Rayleigh criterion, which began in the middle of the last century and continue to the present, confirm it but with some error that does not decrease over the years (with the improvement of the instrument base), which indicates the principle of such an error. In general, the need to position the droplet implies the influence of certain external fields that deform the droplet and, thereby, affect the accuracy of the determined Rayleigh criterion. An experimental and numerical study of the instability of an uncharged drop in an external electrostatic field, the Taylor drop instability, shows its qualitative similarity to the instability of a charged Rayleigh drop. Somewhat apart is the electrohydrodynamic instability of the flat surface of the liquid, the Tonks–Frenkel instability, well studied theoretically but poorly experimentally, due to the fact that high-speed movie cameras have relatively recently entered scientific use.</p>