A randomized study of intestinal decontamination was undertaken in 68 children with leukemia and solid tumours. Framycetin, colymycin, nystatin, and metronidazole were given in 35 neutropenic episodes in 33 children, while co-trimoxazole and lactobacilli preparation were administered in 35 episodes in 35 children. The diseases, severity of neutropenia, and incidence of infection at entry into study were comparable in the two groups. There was no significant difference in the incidence of infections developing during the phase of neutropenia. The median and range of time required to recover from neutropenia were also not different. Co-trimoxazole and lactobacilli were significantly better tolerated, there being no nausea and vomiting, no refusal to take medication, no dose reduction or change to an alternative regimen. We conclude that co-trimoxazole and lactobacilli preparation improve quality of life during a neutropenic episode and have the additional advantage of being relatively inexpensive.