We examined the types of guanine nucleotide-binding regulatory (G) protein subunits in isolated glomeruli, cortices excluding glomeruli and medullas of rat kidneys using bacterial toxin-catalyzed adenosine 5’-diphosphate (ADP) ribosylation and specific immunoblots. ADP ribosylation catalyzed by cholera or pertussis toxin revealed the presence of stimulatory G (Gs) or inhibitory G (Gi) proteins in membranes of the 3 segments of the kidney. Immunoblots further demonstrated the existence of several G-protein subunits, two G<sub>s</sub>-protein α-subunits (G<sub>αs</sub>: 45 and 52 kD), G<sub>i</sub>-protein α<sub>1</sub>, α<sub>2</sub> and α<sub>3</sub>-sub units (G<sub>αi1</sub>, G<sub>αi2</sub>:40–41 kD, G<sub>αi3</sub>: 40 kD), bacterial toxin-insensitive G-protein α<sub>q</sub>- and α<sub>11</sub>-subunits (G<sub>αq</sub>/<sub>11</sub>: 42 kD) and G-protein β-subunits (G<sub>β</sub>: 35-36 kD), in membranes of the preparations. The predominant subspecies of G<sub>αs</sub> was a 52-kD protein in glomerular membranes and a 45-kD protein in membranes of cortices and medullas. All of the G-protein subunits examined, however, were not detected in cytosolic fractions of glomeruli, cortices and medulas. Thus, we conclude that detectable quantities of several G-protein subunits including the new G-protein subunit, G<sub>αq/11</sub>, are present in membranes of glomeruli, cortices not containing glomeruli and medullas from the rat kidney. Both the existence of G<sub>αil</sub> and/or G<sub>αi2</sub> subunits in glomeruli and the presence of G<sub>αq/11</sub> subunits in the 3 preparations are new evidence. Moreover, the current study indicates the existence of the predominant subspecies of G<sub>αs</sub> subunits in the 3 distinct segments of the rat kidney.