The name 'Buffer' does not exist in the current scope

a.ts

///<reference path="node/node.d.ts" />
class A {
  constructor(public b: Buffer) {
  }
}

tsc a.ts

(3,24): The name 'Buffer' does not exist in the current scope

It looks like you have to have the type be "NodeBuffer" rather than "Buffer".

///<reference path="node/node.d.ts" />
class A {
    constructor(public b: NodeBuffer) {
    }
}