  We present observations of the radio emission from the unusual SN 1988Z made
with the VLA from 385 to 4,438 days after explosion. SN 1988Z is the most
distant radio supernova ever detected. The radio light curves are
well-described by a model involving the blastwave interacting with a
high-density circumstellar cocoon, which consists almost entirely of clumps or
filaments. However, at age ~ 1750 days the SN declines much more rapidly than
expected, without a change in absorption parameters. This is due to a change in
the number density of circum- stellar clumps without a change in the average
properties of each clump. This also represents a change in the presupernova
stellar wind properties ~ 10,000 yr before explosion. A massive wind (Mdot >~
10^{-4} Msun/yr) and very high ZAMS mass, ~ 20--30 Msun, is implied for the SN
progenitor, similar to what is likely the case for SNe 1986J and 1998bw.
