The anthelminthic effect of phenylene-diisothiocyanate-(1,4)(=Jonit) was studied on the eighty three cases infected with Ancylostoma duodenale. For the evalution, the number of eggs per gram of feces on all these cases was calculated before treatment. The follow-up for the egg reduction was carried out over a period of four weeks.

The sixty-seven cases were treated in dosage schedule of 3 × 100 mg every 12 hours. The cure rates - the rate of negative conversion of eggs - was 74.6 percent and the total egg reduction rate of 94.2% was obtained.

The ten out of 14 cases treated in the dosage schedule of 2 × 100 mg every 12 hours showed 100% egg reduction and the cure rate was 71.4%. In this group. the total egg reduction rate of 78.6% was noted.

In the dosage schedule of 2 × 50 mg every 12 hours the remainder, two out of total 83 cases showed 100% egg reduction.

Side effects were observed as being mild, 51 cases (56.6%) were free of side reactions and the most frequently noted side effects were vertigo and diarrhea.

From the above results, it is concluded that Jonit is an effective antheminthic against Ancylostoma duodenale and its effectiveness is quite equivalent to that of a known recommended anti-hookworm products.