We use experimental data to obtain a detailed description of individuals' pro-sociality. Participants are faced with a large number of decisions involving variations in the tradeoffs between own and others' payoffs, as well as in other potentially important factors like individuals' positions vis--vis others. We find that decisions are affected by payoff trade-offs in an intuitive way but also by whether individuals obtain more or less than others. We find little reciprocity of the type linked to menu-dependence. The influence of social welfare preferences is stronger than that of difference aversion; however, Leontieff preferences are not more important than difference aversion in our data.