Eggs and larvae from the spotted wolffish (Anarhichas minor Olafsen) were analysed to study the ontogeny of the complement component C3. By Western blotting experiments, the results revealed that C3 was present already in unfertilised eggs and that there was a decrease in C3 content towards hatch, whereas the results using reverse transcription-polymerase chain-reaction showed a continuous increase of C3 mRNA content towards hatch. These findings indicate a transfer of maternal complement component C3 to the offspring where the content of C3 decreases and the level of C3 mRNA increases towards hatch. Immunohistochemical experiments revealed that only the liver of spotted wolffish larvae contained complement component C3, suggesting that the liver is the main site of production.