A recent solicitation over the MEDLIB-L e-mail discussion list revealed ove
r thirty diverse examples of hospital library-based interlibrary cooperativ
e initiatives currently underway. Many are familiar and have been featured
in the professional literature. Most go unreported and unrecognized however
, comprising invisible resource-sharing infrastructures that hospital libra
rians painstakingly piece together in order to provide their clients with e
xpanded service options. This paper, drawing from the MEDLIB-L survey as we
ll as descriptions in the published literature, provides a broad overview o
f such recent interlibrary cooperative efforts. Examples include interlibra
ry loan networks, collective purchasing initiatives, holder-of-record or un
ion catalog access agreements, arrangements to provide e-mail and Internet
access, and consortia to share electronic resources. Examples were chosen b
ased on the initiatives' diversity of participants, and represent a wide ra
nge of locations across the United States. Such initiatives focus on local,
statewide, or regional collaboration, and several involve partnerships bet
ween academic medical center libraries and regional hospital libraries. An
early example of a hospital-based interlibrary cooperative IAIMS effort is
described, pointing to future possibilities involving the Internet and regi
onal hospital system intranets.