Yes. The Sealevel SeaCOM serial driver fully supports interrupt sharing. There are however a couple of points to mention.
All Sealevel PCI serial cards fully support interrupt sharing on Windows 95/98/ME/2000/XP and Vista operating systems. In order for interrupt sharing to work properly, all devices connected to an interrupt must support sharing. If any device or its associated driver is connected to an interrupt and does not support interrupt sharing, then all other devices attempting to share that interrupt will fail.
Sealevel four port (Part# 3405 and 3440) and eight port (Part# 3420) ISA serial boards have special onboard circuitry to support interrupt sharing. The ISA interrupt sharing is supported on these select boards and only with the Sealevel SeaCOM serial driver.