1. Comparative studies of the pharmacological action, especially the toxicity and local irritant properties, was carried out on six compounds which showed marked anthelmintic effect in the foregoing experiments, i.e., 4-n-amylresorcinol (AR), 4-isoamylresorcinol (iso AR), 4-n-hexylresorcinol (HR), 4-n-hexyl-6-chlororesorcinol (HCR), 4-n-octyl-6-chlororesorcinol (OCR), and 4-cyclohexyl-6-chlororesorcinol (CHCR). 2. Oral toxicity in mice, administered as an aqueous suspension, of these compounds were found to be in the order of AR>isoAR>HR>CHCR>HCR>OCR, which agrees with the order of their solubility in water. Principal acute symptom is motor paralysis, and impairment of respiration was the direct cause of death. At times, however, delayed death occurred several days after administration. Oral toxicity was found to be weakened by the addition of olive oil to the chemical. Lethal dose by subcutaneous injection was found to be greater than that of oral administration but the order of LD50 was unchanged. Toxicity on injection into the lymph sac of a frog was in the same order. 3. Slow intravenous injection of CHCR in a rabbit of 2-3 kgm. weight showed that in a dose below 20 mgm./kgm, there were no change in blood pressure or respiration but in 40-50 mgm./kgm. dose, respiration ceased followed by the stoppage of heart beat about 5 minutes later. Artificial respiration administered just before heart failure was successful in reviving the animal. 4. Local irritant action of the six compounds was tested with human tongue, rabbit conjunctiva, shaved skin of a rabbit, and the mucous membrane of the excised dog intestine, and the order of the strength of local irritation agreed well with the foregoing order of toxicity. 5. Administration of 0.2gm./kgm. of the three alylresorcinols in rabbit for five consecutive days failed to give any marked injuries to the gastric membrane but administration of 0.5gm/kgm. of any of these compounds for three days caused erosion, ulceration, and necrosis. 6. Administration of HR as an olive oil solution into the cat stomach with a tube caused death in all three cats tested at 0.3-0.4gm./kgm. dose. The toxicity of other five compounds were greater or lesser than HR, in the same order as in the case of the mouse. The toxic symptom was an ascending paralysis beginning with the hind leg, with a marked restlessness and excitement in the initial period. Acute death was caused by respiration failure and delayed death was more often observed than in the case of the mouse. In acute death, methemoglobin absorption line was seen in the blood of some animals. Toxicity of the aqueous suspension was greater than that of the oil solution. Injuries to the mucous membrane of a cat stomach were reddening, petechial hemorrhage, erosion, and ulceration, in varied degree. The most strongest injury appeared in largest frequencies in alkylresorcinols, and OCR, which had the weakest irritating properties, caused no such injuries even in the same dose as those of the other compounds. 7. Administration of 0.2gm./kgm. in a dog, three times a week for 4-5 weeks, or 0.1gm./kgm. of crystals for 60 consecutive days caused transitory vomiting, loss of appetite, albuminuria, or slight anemia in some animals during the period of administration but no abnormalities were encountered in the others. These symptoms were also more frequent in the two amylresorcinols (AR and isoAR) and were more rarer in the chlorinated derivatives than in HR. Superficial lesion of gastric membrane was observed by 1-3 administrations of 0.05-0.1gm./kgm., but the degree of such injury was much lighter than in the case of a cat. Gastric injuries caused by a long period administration were not necessarily stronger than that caused by a short use. Intestinal injuries chiefly appeared in the duodenum and the large intestines, but in lesser degree than those in the stomach.