There is probably no group of complications which prove to be more baffling to the obstetrician than the toxemias of pregnancy. Certainly they are challenging the best efforts of many earnest investigators, for it is known that the toxemias cause some of the gravest conditions that arise during pregnancy, and they are suspected of being the underlying cause of still others which are as yet unaccounted for. Comparatively little is known of the origin of the toxemias, except that they are due to pregnancy. But happily, a good deal is known about preventing them, and also about relieving them, particularly in the early stages; accordingly many mothers and babies are saved who otherwise would perish. The entire subject of the prevention and treatment of these disorders will be somewhat simplified for the nurse if she will recall the general question of the adaptations of the mother’s physiology during pregnancy. She will then remember that there were certain alterations of function which were necessary to keep the maternal organism normal, while it bore the strain of supplying nourishment to the fetus from its own blood stream, and received in turn the broken-down products of fetal activity. If these adaptations are insufficient to meet the demands made upon the maternal organism, a serious toxic condition may result. To put the matter briefly, there is in the toxemias of pregnancy a disturbance of the mother’s metabolism, involving the liver and kidneys, and a resulting retention within her body of something which should be excreted. The retention of this material, which may be of fetal or maternal origin, or both, may give rise to symptoms which range anywhere from slight headache or nausea to coma, convulsions and death. Beyond these general facts, there seems to be deep obscurity concerning the cause of this group of complications, of which _pernicious vomiting_, _pre-eclamptic toxemia_ and _eclampsia_ are the most widely and generally recognized. While _nephritic toxemia_ and _acute yellow atrophy_ of the liver cannot be designated, quite accurately, as toxemias due to pregnancy, they are usually included in this group. This may be because they are toxemias which have many features in common with those of pregnancy, as to symptoms and treatment, and because of the frequency with which they appear coincidently with pregnancy, although not always due primarily to that state. From the nurse’s standpoint, it will perhaps be as well to regard all of the toxemias of pregnancy as manifestations of the same general disturbance, which vary according to the stage of pregnancy at which they appear, and which differ from each other chiefly in severity, or degree, rather than in kind.