The research focused on variations in aggressiveness between ethnic groups among participants in two Kid Clubs (Havenhearst and Santa Fe) in a Southern California community. The mission of Kid Clubs is to promote and reinforce the attributes of self-esteem and self-assurance while providing children with fundamental leadership experiences and skill-development opportunities. Data were collected by using extended observations as well as focused and unstructured interviews with informants and interactants. A total of 53 site visits were conducted at Havenhearst and 44 site visits at Santa Fe. Field notes and a daily diary were kept for each site visit. More than 400 aggression operations were observed and recorded at Santa Fe and Havenhearst. Although each aggressive operation was singular, certain types of aggressive behavior apparently clustered based on meaning, action, and operation. An important setting variation between Havenhearst and Santa Fe was the dearth of verbally aggressive greeting operations observed at Santa Fe. African-American males consistently greeted one another with aggression referred to as mock-battle greeting posturing; for example, a male African-American participant meeting a peer might face the other in close proximity, pull away, and take a fighting stance, and then utter a combative challenge. The challenged male would strike at the air near the "aggressor's" face while the other returned the mock blows; then they shook hands or embraced and proceeded to an activity together. The greeting posturing observed among Latino and Euro-American males did not include ritualistic mock-battle posturing greetings. Data from this study thus show that staff members and youthful participants promote activities and a culture in which aggressiveness served a prosocial communication function through negotiated meanings. Verbally aggressive greetings and ritualistic mock-battle greeting aggressiveness among males can be viewed as discrete cultural communication codes among the African-American participants. Although these greeting rituals are not understood by the participants as an intent to harm, the operation can easily be misunderstood by others. Service providers should be aware of unique communication styles in the communities where they work and the potential effects of communicative codes, so as to avoid miscommunication. Implications are drawn for future research. 1 figure and 41 references