We compared vasoconstrictor response times to sympathetic nerve stimulation (SNS) as well as autoregulatory responses (AR) to a 20 mmHg step increase of perfusion pressure in the kidney and hindlimb of anesthetized rats. SNS of renal and lumbar nerves (1–8 Hz for 60 s) led to similar reductions in renal (RBF, -59% at 8 Hz) and iliac blood flow (IBF, -64%). RBF fell biphasically with a rapid component within 3–5 s ([tau]=3.0 s) and a slower one over 30–50 s (t=11 s), both contributing equally. In contrast, IBF fell monophasically within 3–5 s (t=1.5 s). Dynamic SNS (~5 Hz, Dt on, Dt off, Dt=1, 2, 3, 4, 8, 15, 60 s) showed similar corner frequencies for RBF and IBF at ~0.15 Hz and an additional one for RBF at ~0.05 Hz. AR was bimodal in RBF with a fast initial response within 9 s ([tau]=3.3 s) providing 38% AR efficiency, and a subsequent slower response within 30–120 s. AR in IBF was monophasic ([tau]=2.5 s) providing 34% AR. It is concluded that the fast components of SNS and AR vasoconstrictor responses are of similar speed in kidney and skeletal muscle. Secondary slower mechanism(s) operate in the kidney slowing the overall RBF adaptation. Whether the latter also reflect tubuloglomerular feedback as in AR awaits further study. Supported by NIH (HL02334) and Guyton Award for Excell. in Integr. Physiol