There is increasing demand for high quality, biologically active recombinant proteins in awide range of applications, from simple positive controls for immunoassays to complex virus like particles (VLPs) as sub unit vaccines. Baculoviruses have been employed for over 30 years to make recombinant proteins. One of the most popular systems currently used to make recombinant baculoviruses is flashBAC. This utilizes a one step process whereby a plasmid transfer vector with a foreign gene is mixed with flashBAC and used to cotransfect insect cells. Five days later, a virus containing the gene is available for making recombinant protein to very high levels in virus-infected cell cultures. This system has also been tailored to optimise the production of particular types of protein. flashBACGOLD maximises production of membrane-bound (e.g. receptors) or secreted proteins (e.g. urokinase) owing to deletion of chitinase and cathepsin genes, whose products limit transport through the endoplasmic reticulum and promote protease activity. Another variant, flashBACULTRA lacks the virus p10 gene as well as chitinase and cathepsin, which decreases virus-infected cell lysis in the later stages of infection and contamination of recombinant protein preparations with cellular debris. Both of these flashBAC variants are ideal for producing VLPs (e.g. influenza virus) that bud from the plasma membrane. Conversely, for VLPs that remain intracellular and are protease resistant, it can be advantageous to use flashBACPRIME, which retains chitinase, cathepsin and p10. This ensures that the virus-infected cells lyse in the terminal stages of replication and release VLPs that are easy to purify.