Interview data were collected in May-July 1995 and focused on serious property crimes and violent offenses. Information on dependent variables, several measures of criminal involvement, was obtained through self-reports. Independent variables included formal sanctions and informal control. Findings revealed many street youth feared legal sanctions but more serious offenders did not. Instead, fear of punishment was reduced by poverty, drug use, association with criminal peers, and missing normative constraints. Serious street youth offenders were immersed in a lifestyle in which crime, drugs, and criminal peers fed off each other and isolated these offenders from conventional society. Poverty, homelessness, peer support, and conventional commitments influenced perceptions of threatened formal sanctions but did not exhibit any direct effects on crime. The authors suggest traditional models of deterrence must be re-examined when dealing with at-risk groups. 81 references, 7 notes, 3 tables, and 1 figure