1. Unidirectional electrostimulation was therapeutically applied in convulsive doses to 176 hospitalized psychiatric patients. The present report covers 2,746 convulsive reactions induced through left temple (negative), vertex-of-skull (positive) electrode placements.2. The threshold convulsive dose, expressed in milliampere-seconds (product of intensity and duration of stimulation), was determined for four different types of unidirectional electrostimulation. The technique for obtaining threshold convulsive doses was described.3. Type A. 1. stimulation consisting of rectified waves at 60/sec., each wave lasting 1/120 sec. with intervals of 1/120 sec. was tried in 154 instances. Practically 68 per cent of the trials gave convulsive thresholds at 50 mA.-sec. or less, with 45 per cent requiring intensity level of 46-60 mA.4. Type A. 2. stimulation, designated as type A. 1. waves interrupted by a make commutator at 10/sec. giving rise to impulse bursts of 1/20 sec., was tried in 1,735 instances. In 83 per cent of the trials the convulsive dose was 50 mA.-sec. or less with 52 per cent in the 26-50 mA. sec. group and 31 per cent requiring 1-25 mA. sec. The intensity level was in the 16-30 mA. group in over 70 per cent of the trials.5. Type C. 2. stimulation is described as 10/sec. commutator interrupted type C. 1. wave form. Type C. 1. is a 60/sec., slightly smoothed (filtered) rectified wave form, each wave lasting 1/6o sec. with no interval. of the 270 convulsive doses by type C. 2. stimulation, 66 per cent occurred at 50 mA.-sec. or less, with the intensity level in the 16-30 mA. group in 72 per cent of the trials.6. Type C. 3. stimulation, described as the type C. 2. form further interrupted by rapid manipulation of the hand switch, was given 587 trials. Of these, practically all occurred at doses of 50 mA. sec. or less, with 80 per cent at 1-25 mA. sec. This markedly low convulsive dose more than offset the higher intensities required (46-90 mA. in 82 per cent of the trials).7. Unidirectional electrostimulation seemed to offer convulsive doses markedly less than required by techniques utilizing the alternating current.