If your database is in FULL or BULK_LOGGED recovery model, and you are not running transaction log backups, then your transaction log file will continue to grow until the next full backup is performed.
Transaction log backups are recommended in FULL or BULK LOGGED recovery models.
You might ask, would it be better to just switch the database to simple recovery model? The answer is YES, it would certainly be simple, however, probably not the best choice. Transaction logs could be turned on to be sure that you have frequent backups, and so that you will not bloat out the transaction log files.