EUGENE A. WRIGHT, Circuit Judge:
Defendant appeals from a judgment for plaintiffs who sued to recover on a personal guaranty. Appellant Overmyer, a New York resident, was chairman of the board and sole stockholder of D. H. Overmyer, Inc. (Ohio) [hereafter Ohio, Inc.], an Ohio corporation. Ohio, Inc., in turn, was the 100% owner of D. H. Overmyer, Inc. (Oregon) [hereafter Oregon, Inc.], an Oregon corporation. Appellant also was the chairman of the board and the chief executive officer of Oregon, Inc. His guaranty of certain obligations of Oregon, Inc. was the subject of the suit.
OPINION
I.
FACTS
Plaintiffs learned from a California real estate broker that a warehouse in Oregon, owned by Oregon, Inc., was available for sale and lease back. Forsythe indicated some interest in it.
For several days, Forsythe and his attorney met with J. R. Fitzsimmons, an attorney and assistant secretary of Ohio, Inc., parent of Oregon, Inc. As a condition of the proposed purchase and lease, Forsythe insisted that Overmyer personally guarantee performance of Oregon, Inc.’s obligations as lessee. Fitzsimmons telephoned Overmyer in New York to inform him of Forsythe’s insistence on a personal guaranty. Overmyer responded by telegram from New York to Forsythe in California, confirming his willingness to give the guaranty. Overmyer then executed the guaranty and forwarded it by mail to Forsythe.
The lease, but not the guaranty, provided that it would be subject to the jurisdiction of California courts and that California law would govern. Oregon, Inc. failed in its obligations as lessee. Late in 1973, Ohio, Inc., along with its numerous subsidiaries, including Oregon, Inc., filed petitions in bankruptcy under Chapter XI. Virtually all Overmyer corporations were in substantial arrears to landlord purchasers.
In October, 1973 plaintiffs sued on the guaranty1 and, after Overmyer’s motion to dismiss for lack of personal jurisdiction was denied, the case went to trial.2 The court granted judgment for plaintiffs, for $90,-618.17, with 7% interest from the date of judgment and attorney’s fees of $11,796.38. On appeal, Overmyer challenges the jurisdiction of the district court.
II.
NO. 75-2855
A. J urisdiction.
Plaintiffs have the burden to establish jurisdiction. KVOS, Inc. v. Associated Press, 299 U.S. 269, 278, 57 S.Ct. 197, 81 L.Ed. 183 (1936). Upon a motion to dismiss for lack of personal jurisdiction, the burden varies according to the nature of the pre-trial proceedings in which the jurisdictional question is decided. Data Disc, Inc. v. Systems Tech. Assoc., 557 F.2d 1280, 1285 (9th Cir. 1977). Whatever degree of proof is required initially, a plaintiff must have proved by the end of trial the jurisdictional facts by a preponderance of the evidence.
1
In a suit against Oregon, Inc., an Oregon state court awarded plaintiffs a judgment for rent, property taxes, interest and attorneys’ fees.
2
Trial was to the court on affidavits.