This work is concerned with the problem of scheduling with agreements (SWA in short). This consists in scheduling a set of jobs non-preemptively on identical machines, subject to constraints that only some specific jobs can be scheduled concurrently. These constraints are represented by an agreement graph. The goal is to minimize the makespan. We generalize some old NP-hardness results of the class of bipartite agreement graphs with two machines. The complexity of both split and complement of bipartite agreement graphs is also considered. Some polynomial cases for both classes are presented. Then we establish approximation results for the SWA problem. All of these results are oulined below.