Differential rotation arises from the interaction between convection and rotation, so it is believed to exist in all the stars with a convective envelope. In a turbulent convection zone differential rotation is expected to be a central element of stellar activity, in fact the shearing motions of different layers wind up the magnetic field lines, governing the magnetic cycle and all the activity phenomena (as starspots, chromospheric CaII emission, X-ray emission). There are three different methods used for the measurements of the degree of differential rotation, e.g. variation of rotational periods, Doppler imaging and line profile analysis. I will focus here on the latter, showing how the Fourier transform method works and making an overview of the results obtained so far. Differential rotation seems to correlate with many stellar parameters, as rotational velocity and spectral type. Being a very important feature in all stars with a convective envelope, it can be used to check some of the many models describing the convection zone.