Human concern for environment began as a reaction to single episodes of damage to environment and human health. As a consequence, today, the assessment of environmental impacts consists mostly of negative externalities. When social and economic aspects were considered together with environmental aspects to assess sustainability, the tradition of looking for negative externalities has continued. However, when considering satisfaction of human needs, which is the ultimate goals for sustainable development, it becomes obvious that there are many positive externalities that are not taken into account. Capacity and efficiency to satisfy basic human needs characterize such externalities.