The object of this paper is to develop sliding mode control design methods for infinite-dimensional systems. The unit control method was introduced for finite-dimensional systems by S. Gutman [IEEE Trans. Autom. Control AC-24, 437-443 (1979; Zbl 0416.93076)] and by S. Gutman and G. Leitman [|Optim. Tech., Part 2, Proc. 7th IFIP Conf., Nice 1975, Lect. Notes Comput. Sci. 41, 729-755 (1976; Zbl 0334.93030)]. Since the unit control has as advantage that it only changes on manifolds, it can be extended to infinite-dimensional spaces. This is in contrast with conventional component-wise control. The methods are illustrated by designing a control for heat and mechanical distributed processes operating under uncertainty conditions.