SLAT MALFUNCTION.

Narrative

AFTER DEPARTING STL FOR SFO; AND AFTER RETRACTING GEAR AND FLAPS THEN CLBING THROUGH 5000 FT; THE LEADING EDGE IN-TRANSIT LIGHT CAME ON. THERE WERE NO OTHER INDICATIONS ON THE ENGINEER'S PANEL. WE VISUALLY CONFIRMED THAT THE LEADING EDGE DEVICES WERE INDEED EXTENDED. WE CONTINUED CLBING AND MAINTAINED LESS THAN 250 KTS. WE LOWERED THE FLAPS TO 40 DEGS. THE IN-TRANSIT LIGHT WENT OUT; AND THE LEADING EDGE EXTENDED R (GREEN) CAME ON. ON THE ENGINEER'S PANEL; ALL THE 14 GREEN LIGHTS CAME ON; AND THE SLAT POS INDICATOR WENT THEN TO 30 DEGS. WE THEN RAISED THE FLAPS. THE TRAILING EDGE FLAPS CAME UP; BUT THE LEADING EDGE IN-TRANSIT LIGHT CAME ON AGAIN; AND REMAINED ON. THE MAJORITY OF THE 14 GREEN LIGHTS REMAINED ON. THERE WAS NO ADVERSE ROLL. THE LEADING EDGE DEVICES REMAINED EXTENDED. WE LOWERED AND RAISED THE FLAPS ONE MORE TIME; BUT WITHOUT SUCCESS. WE WENT THROUGH ALL THE PERTINENT CHKLISTS TO LOCK THE SLATS DOWN; RETURNED TO STL AND DID AN OVERWT LNDG (362000 LBS) WITH NO PROBS. IT WAS A SMOOTH; GENTLE LNDG. WE DID NOT DECLARE AN EMER.