Eleven cell lines were prepared from skin, snout, liver, kidney, lung, heart, brain, spleen, thyroid, urinary bladder, and periorbital soft tissue of a juvenile Hawaiian monk seal (Monachus schauinslandi). The cell grew at 37 degrees C in RPMI 1640 medium supplemented with 20% fetal bovine serum. These cell lines have been subcultured 11-27 times since their initiation in May 1997. Growth of the monk seal cells was serum-dependent and plating efficiencies ranged from 4-24%. These monk seal cells grew well in M199, L-15 and MEM commonly used for cultivation of animal and mammalian cells and retained 87% cell viability following storage for 2.5 years in liquid nitrogen. Karyotyping indicated that these monk seal-derived cell lines remained diploid with a chromosome count of 34 at their early passage (passage 9-13). These cell lines were tested for herpesvirus by polymerase chain reaction using degenerate oligonucleotide primers designed from the highly conserved region of herpesviral DNA polymerase gene and no specific detection occurred. These newly established cell lines are currently being used for the investigation of an eye disease occurring in captive monk seal pups in Oahu and will be available for future isolation and study of monk seal viruses.