A monolayer culture of fibroblast-like cells was initiated and established from a trypsin digest of Omaka fish larvae (Caranx mate). The cell culture has been subcultured 105 times over a period of 30 mo and appears to be contact-inhibited. The Omaka cells grew optimally at 27 degrees in Eagle's basal medium plus 10% fetal calf serum but failed to grow at 16 and 37 degrees. At the lower temperature the cells remained viable and began to divide when the temperature was raised to 27 degrees. Unlike certain marine fish cell lines the Omaka cell did not require a higher osmolarity medium for optimal growth. Karyological analysis at the 43rd passage revealed a chromosomal modal number of 50 consisting of 7 submetacentric pairs and 18 acrocentric pairs of chromosomes. Virological studies indicated that Omaka cells supported the replication of poikilothermic viruses such as, FV-3 and IPN viruses, but not the mammalian viruses examined. Attempts to induce interferon by the synthetic polynucleotide poly I:C were unsuccessful.