Syntax:
RESET SLAVE

RESET SLAVE makes the slave forget its replication position in the
master's binary log. This statement is meant to be used for a clean
start: It deletes the master.info and relay-log.info files, all the
relay log files, and starts a new relay log file. To use RESET SLAVE,
the slave replication threads must be stopped (use STOP SLAVE if
necessary).

*Note*: All relay log files are deleted, even if they have not been
completely executed by the slave SQL thread. (This is a condition
likely to exist on a replication slave if you have issued a STOP SLAVE
statement or if the slave is highly loaded.)

Connection information stored in the master.info file is immediately
reset using any values specified in the corresponding startup options.
This information includes values such as master host, master port,
master user, and master password. If the slave SQL thread was in the
middle of replicating temporary tables when it was stopped, and RESET
SLAVE is issued, these replicated temporary tables are deleted on the
slave.

URL: http://dev.mysql.com/doc/refman/5.0/en/reset-slave.html

