We review recent observational and theoretical results on the relationship
between circumstellar accretion disks and jets in young stellar objects. We
then present a theoretical framework that interprets jets as accretion-powered,
centrifugally driven winds from magnetized accretion disks. Recent progress in
the numerical simulation of such outflows is described. We also discuss the
structure of the underlying magnetized protostellar disks, emphasizing the role
that large-scale, open magnetic fields can play in angular momentum transport.