S CDM). Thus 8.1 `tie-breaker' VL tests at immunological/clinical failure would be needed to prevent one switch with suppressed VL. Fewer participants switching for CD4,100 cells/mm3 had VL,400 copies/ml (7 ) than those meeting other CD4 or clinical criteria (p = 0.03). Those with CD4,100 cells/mm3 had a very wide range of VLs (Figure 1(b)), similarly to participants monitored without CD4s. In tho