Based on available surface area for cell attachment, a 15 l culture is equivalent to approximately 388 × 850 cm 2 roller bottles in terms of potential virus production (Table 1) . A typical growth curve for CR2 cells on Cytodex 1 microcarriers grown at the 15 l scale is shown in Figure 7 . Cells multiplied exponentially during the first 6 days before reaching stationary phase. Typically a cell density of 4.0-5.0 × 10 10 total cells was obtained after approximately 150 h. After this growth period a confluent monolayer of CR2 cells (Figure 3 ) covered the microcarriers. When the cells exhibited complete CPE (Figure 4 ) 60-72 h after infection, the cultures were harvested. Infectious DISC-HSV released from the CR2 cells was quantified using a TCID 50 assay and was again compared to the titre achieved from the equivalent roller bottle culture harvests. The results are shown in Table 1 . Typically 4-7.0 × 10 11 total pfu from a 15 l culture was achieved, with a period of approximately 9 h during which this high titre was sustained. From an equivalent number of 388 roller bottles we would expect to achieve approximately 3.88 × 10 11 total pfu. Our results, therefore, compare very favourably with the expectations from roller bottle cultures and the results achieved from the 1 l cultures.