An analysis is given of Coulomb collisions, which are the dominant collisional process that occurs in hot plasmas. We show that Coulomb collisions are dominated by small-angle grazing collisions, much different than collisions in a normal gas, which are almost always nearly isotropic. For such small angle collisions, the impact cross-section is dominated by large impact parameters. Because of Debye shielding the impact cross-section has an upper limit given by the Debye length. The small-angle scattering and the exponential cutoff of the impact cross-section caused by Debye shielding makes the analysis of collisional effects quite complicated. As an example, the collisional drag force acting on a Maxwellian velocity distribution of electrons drifting through a background of fixed ions is analyzed. The results show that the drag force on the electrons initially increases linearly with increasing drift velocity, reaches a maximum near the electron thermal velocity, and then decreases rapidly. When the drift is caused by an applied electric field this dependence leads to an upper limit, called the “Dreicer field,” beyond which the electrons accelerate without limit.