A portable electronic device with a touch screen display displays a list of instant messaging conversations including a group conversation. The group conversation includes a first multi-recipient identifier and a group conversation indicia. In response to detecting a user selection of the group conversation, the device displays a set of outgoing messages from a user of the device to multiple recipients in a chronological order and a second multi-recipient identifier. The device receives a new outgoing message for the group conversation entered by the user of the device through the touch screen display, and responds to detecting a user request to send the new outgoing message to the multiple recipients by sending the new outgoing message to the multiple recipients in the group conversation. The new outgoing message is appended to the set of outgoing messages displayed on the touch screen display.