We consider a way to associate a language with the computations of a tissue P system. We assign a label to every rule, where the labels are chosen from an alphabet or the label can be λ. The rules used in a transition should have either the empty label or the same label from the chosen alphabet. In this way, a string is associated with each halting computation, called the control word of the computation. The set of all control words associated with computations in a tP system form the control language of the system. We study the family of control languages of tP systems in comparison with the families of finite, regular, context-free, context-sensitive, and recursively enumerable languages. © 2013 Springer-Verlag Berlin Heidelberg.