Table of Contents

On the theory of unipotent algebraic groups over an arbitrary ground field.- Notations, conventions and some basic preliminery facts.- Forms of vector groups; groups of Russell type.- Decomposition theorems for central extensions of co utative group schemes; application to the two-dimensional unipotent groups.- Wound unipotent groups.- The question of commutativity for two-dimensional unipotent groups.- Forms of the affine line and geometry of the groups of Russell type.- Actions of unipotent group schemes.- The underlying scheme of a unipotent algebraic group.- The hyperalgebra of a unipotent group scheme.