Objective: The inefficient management of trash causes one of the most important pollution problems we find, caused by city managers inefficient of approach. They invest in technology, without regard for citizen participation. Thus the objective of this paper was to establish the factors that make easy or inhibit trash separation at home, comparing two different cities Background literature: We used Pol's (2001) four spheres model, making a comparative study about the variables involved in the acquisition, handling and removal of solid waste by the people. Method: A non-probabilistic, two stage sampling was carried out. The first stage drawn from Barcelona's population and the second with Mexico City's one. The sample was constituted by 1105 subjects, 400 from Barcelona and 705 from Mexico City. Of them, 64%were women and 36% men. In both cities a 56 item questionnaire was applied. Findings & conclusions: Age correlated positively with the amount of separated materials. .With an analysis of variance we established that the amount of trashcans and having friends that separate trash were influential variables. In Barcelona the model explains 33% of the variance and in Mexico City 25%. In Barcelona the percentages of separation show that the behavior is related to the management system, as compared to Mexico City, where the cultural tradition explains it. Conclusions Within the houses, what is most important are the way space is used and not space by it self. This has incidence on separation, thus the work on ergonomic design of kitchens has to keep going. Not every thing can or has to be managed, there must be a space for people involvement and participation; as generating an image of efficiency of the administration generates lack of responsibility feelings from the people. Applicability & the work to done next: A good management must dignify working with trash and must generate jobs; it must integrate non formal jobs through legalization, investing more on wages rather than in technological infrastructure that becomes obsolete in a spell. You have to make a participant design that takes in account the context and that necessarily implies having several systems. You also have to promote the flea markets (tianguis), where objects are revalued. It is suggested that research has to be extended inquiring forms in which responsible consumption are promoted.