RZ Sgr is the sole S star and the only lithium-rich star
 known to be associated with visible nebulosity. It thus
 provides us with a unique opportunity to trace the mass-loss
 history of an Asymptotic Giant Branch (AGB) star over a
 significant fraction of its thermal pulsing lifetime. Current
 evidence suggests that RZ Sgr is a low-mass star, making it a
 particularly interesting individual object because there is,
 as yet, no theoretical understanding of the process of
 lithium enrichment among low-mass stars. We propose a
 detailed study of this star and its nebula using the ISO
 instrumentation.