Starting with an overview of the various requirements placed on substr
ates for superconducting microwave applications, the current state of
the art of high temperature superconducting thin films on different su
bstrate types is discussed. Recent results for several superconducting
microwave components that could form important building blocks for ad
vanced microwave systems are presented, including performance data on
experimental devices such as narrow band-pass and band-stop filters, s
uperconducting circulators and miniature, low-frequency spiral resonat
ors. Some examples of system types that can most likely benefit from h
igh temperature superconductivity are identified.