The change in the current scenario due to the increasing concern about environmental issues, has underlined the need for new destinies for the waste we produce, as well as seeking the reduced production of these wastes. This greater awareness of people and their participation in environmental actions are fundamental to solve the problem of disposal of solid waste. Every year the population consumes millions of products and generates millions of tons of waste that are not correctly destinated, because people didn´t make the correct separation of this material, motivated by a lack of interest or knowledge on the subject. To make effective the selective collect and waste recycle, the resident must do their part by separating garbage at his residence. This study aimed to identify the predominant factors of the BDI Model (BRATMAN, 1999) in the behavior of adequate separation of household waste from residents of Porto Alegre. We conducted 546 online questionnaires, collected through social networks and contacts of the researchers. The results of the factor analyzes performed point to the predominance of the belief in the explanation of individual behavior about separating waste.