The invention relates to a process for preparing microspheres comprising an ionically crosslinked polymer, the process comprising: (a) producing liquid aerosol droplets (13) from a solution (3) comprising an ionically crosslinkable polyionic polymer into a continuous gas stream by using an ultrasonic nebulizer; (b) transferring the gas stream into a gelling solution (10) comprising di-, multi- or polyvalent ions, whereby crosslinked polymer microspheres (14) are formed, (c) separating the microspheres from the gelling solution, and (d) optionally, filtering the microspheres through a screen.