1 Model checkers for systems represented by labelled transition systems are not as extensively used as those 2 for systems represented by Kripke structures. This is partially due to the lack of an elegant formal language 3 for property specification which would not be as raw as, for example, HML yet also not as complex as, for 4 example, µ-calculus. This paper proposes a new action-based propositional branching-time temporal logic 5 ACTLW, which enhances popular computation tree logic (CTL) with the notion of actions in a similar but 6 more comprehensive way than action-based CTL introduced by R. De Nicola and F. Vaandrager in 1990. 7 ACTLW is defined by using temporal operators until and unless only, whereas all other temporal operators 8 are derived from them. Fixed-point characterisation of the operators together with symbolic algorithms for 9 global model checking are shown. Usage of this new logic is illustrated by an example of verification of 10 mutual-exclusion algorithms.