We present in this paper a 5/2-approximation algorithm for scheduling rigid jobs on multi-organizations. For a given set of n jobs, the goal is to construct a schedule for N organizations (composed each of m identical processors) minimizing the maximum completion time (makespan). This algorithm runs in O(n(N +log(n)) log(npmax)), where pmax is the maximum processing time of the jobs. It improves the best existing low cost approximation algorithms. Moreover, the proposed analysis can be extended to a more generic approach which suggests different job partitions that could lead to low cost approximation algorithms of ratio better than 5/2. 1 Problem statement In this paper we consider the problem of scheduling rigid jobs on Multi-organizations. An organization is a set of m identical available processors. A job j must be executed on qj processors (sometimes called the degree of parallelism) during pj units of time. The qj processors must be allocated on the same organization. The makespa...