Reports 2 field and 2 laboratory experiments on littering behavior. In Exp I, observations of 1,765 Ss at 9 locations in the New York City area showed that littering rates varied substantially across areas of a large urban region and that the rate for a particular area was correlated with the amount of litter already present. It was also found that males littered more than females, and young people more than old. In Exp II, a laboratory experiment, a causal relationship between the amount of litter in an area and the likelihood it will be littered was demonstrated by data from 60 undergraduates. Exp III, with 35 undergraduates, replicated this latter finding, but did not find a relationship between the amount of stress experienced by an S and the likelihood that he or she would litter. In Exp IV, a field experiment, Ss who were approached and asked to sign a petition about clean streets littered less than control Ss.