We report the expression and production of llama variable heavy-chain antibody fragments (VHHs) by Aspergillus awamori. Fragments encoding VHHs were cloned in a suitable Aspergillus expression vector and transformants secreting VHH fragments were analysed for integrated gene copy-numbers, mRNA levels and protein production. Functional V HHs were detected in the culture medium, indicating the feasibility of producing this type of protein in a fungal expression system. Secreted V HHs were subjected to (extracellular) degradation, which could be partially prevented by the addition of BSA to the culture medium. © Springer-Verlag 2004.