The reversal of vecuronium paralysis was studied in three series of anesthetized (methohexital, fentanyl, N2O/O2) informed adult patients receiving either 40 micrograms/kg neostigmine (NEO40) (n = 6), either 500 micrograms/kg edrophonium (EDRO500) (n = 6) or 1000 micrograms/kg edrophonium (EDRO1000) (n = 6). These drugs were given randomly once the adductor pollicis twitch height regained 10% of its initial value. The neuromuscular transmission recovery was assessed during 15 minutes after the antagonist administration, by recording twitch height (TH), train of four--2 Hz--every 3 minutes (TOF Ratio) and finally tetanic fade--50 Herz (TET50) and 100 Hz (TET100), 5 seconds duration, one minute apart--. At 15 minutes, the TH values (mean +/- SEM) were for EDRO500 92% +/- 7, for EDRO1000 93% +/- 3 and for NEO40 100% +/- 4 percent (n.s.). For the TOF Ratio, a statistical difference (p less than 0.05) was found between NEO40 86% +/- 4 and the two other groups: EDRO500 73% +/- 3, EDRO1000 69% +/- 4. For the TET50, the values were: EDRO500 93% +/- 3, EDRO1000 86% +/- 5 and NEO40 94% +/- 2 (n.s.). At 100 Hz, the values were: NEO40 61% +/- 8, EDRO500 43 +/- 151 and EDRO1000 31 +/- 12 (p less than 0.01). In conclusion, in the conditions studied, 40 micrograms/kg neostigmine restores the neuromuscular transmission of the adductor pollicis at a higher level than edrophonium 500 micrograms/kg does. Edrophonium, 1000 micrograms/kg instead of 500 micrograms/kg does not change the neuromuscular transmission recovery.