A plaintiff may serve a party as a doe defendant under CCP 474 if, at the time the original complaint was filed, the plaintiff did not have actual knowledge of the person’s name or of the facts giving rise to a claim against him. Mere suspicion or constructive knowledge is not sufficient to bar use of the doe defendant mechanism. However, here, the trial court properly found that the plaintiff did have actual knowledge that Coblentz, a lawyer, conducted his business as trustee of the McClatchy trust in the Coblentz law firm’s office, using its stationery. Furthermore, plaintiff learned no added facts after filing his original complaint and before the doe amendment which added to his theory of liability against the law firm for Coblentz’s alleged misdeeds as trustee. So either he knew he had a viable claim against the law firm from the beginning or he never had a viable claim, and in either event the doe amendment was improper. An improper doe amendment may be attacked by a motion to quash service of process on the newly named defendant, but granting the motion does not prevent the plaintiff from amending the complaint to rename the same person as a regular defendant and asserting against him all claims still not barred by the statute of limitations.