Hypoproteinemia is generally considered to form a threat to blood volume homeostasis. In conscious splenectomized dogs we studied whether severe hypoproteinemia, in the presence or absence of edema, would compromise the early recovery of blood volume after moderate hemorrhage (congruent to 25%). Hypoproteinemia, achieved by 10 days of repeated plasma exchange and a low-protein diet, did not induce a fall in steady-state blood volume. The interstitial colloid osmotic pressure decreased, an adaptive response probably playing a major role in this maintenance of blood volume. Within the first 2 hr after hemorrhage blood volume recovered by about 30% of the hemorrhaged volume. This early recovery of blood volume was enhanced rather than impaired in hypoproteinemia, in particular in the presence of edema. Since circulating protein did not increase within this 2-hr period, acute fluid attraction occurred through transcapillary influx of interstitial fluid. Chronic hypoproteinemia apparently enhances this fluid attraction. This may be explained by the low interstitial fluid oncotic pressure and fluid expansion, thus by those very factors directed to maintain blood volume in hypoproteinemia.