A computer-implemented method, comprising: at a portable electronic device with a touch screen display: displaying a set of messages (604, 606) exchanged between a user of the device and another person in a chronological order; detecting a scrolling gesture comprising a substantially vertical movement of a user contact with the touch screen display, wherein the detecting of the scrolling gesture is substantially independent of a horizontal position of the user contact with the touch screen display; and responding to the scrolling gesture by scrolling the display of the set of messages in accordance with a direction of the scrolling gesture, further comprising: concurrently displaying: the set of messages exchanged between the user and the other person in a message display region; and a text box and a first set of keys in a message compose region; while concurrently displaying the set of messages, text box and first set of keys, detecting a user selection of one or more of the first set of keys; in response to detecting a user selection of one or more of the first set of keys: displaying a word fragment in the text box in accordance with text entered by the user; and displaying one or more text entry suggestions in the message compose region in accordance with the text entered by the user, wherein the one or more text entry suggestions represent a respective completion of the word fragment; upon detecting a predefined user gesture corresponding to a respective text entry suggestion of the one or more text entry suggestions, replacing the word fragment in the text box with the respective text entry suggestion; receiving a selection input directed to a respective position in the message compose region to send a new message; in response to receiving the selection input directed to the respective position in the message compose region: sending the new message that includes the respective text entry suggestion; displaying the set of messages exchanged between the user of the device andanother person with the new message in chronological order. displaying a set of messages (604, 606) exchanged between a user of the device and another person in a chronological order; detecting a scrolling gesture comprising a substantially vertical movement of a user contact with the touch screen display, wherein the detecting of the scrolling gesture is substantially independent of a horizontal position of the user contact with the touch screen display; and responding to the scrolling gesture by scrolling the display of the set of messages in accordance with a direction of the scrolling gesture, further comprising: concurrently displaying: the set of messages exchanged between the user and the other person in a message display region; and a text box and a first set of keys in a message compose region; the set of messages exchanged between the user and the other person in a message display region; and a text box and a first set of keys in a message compose region; while concurrently displaying the set of messages, text box and first set of keys, detecting a user selection of one or more of the first set of keys; in response to detecting a user selection of one or more of the first set of keys: displaying a word fragment in the text box in accordance with text entered by the user; and displaying one or more text entry suggestions in the message compose region in accordance with the text entered by the user, wherein the one or more text entry suggestions represent a respective completion of the word fragment; displaying a word fragment in the text box in accordance with text entered by the user; and displaying one or more text entry suggestions in the message compose region in accordance with the text entered by the user, wherein the one or more text entry suggestions represent a respective completion of the word fragment; upon detecting a predefined user gesture corresponding to a respective text entry suggestion of the one or more text entry suggestions, replacing the word fragment in the text box with the respective text entry suggestion; receiving a selection input directed to a respective position in the message compose region to send a new message; in response to receiving the selection input directed to the respective position in the message compose region: sending the new message that includes the respective text entry suggestion; displaying the set of messages exchanged between the user of the device andanother person with the new message in chronological order. sending the new message that includes the respective text entry suggestion; displaying the set of messages exchanged between the user of the device andanother person with the new message in chronological order.