The presence of Δ2-3 somatic transposase to Muller5-B X chromosome carrying five target P-elements causes pupal lethality, with or without heat shock P{S-UP3} can repress some of the lethality. P{S-UP3} fails to repress gonadal dysgenesis, either through a maternal effect or through a combination of zygotic and maternal effects, with or without heat shock. P{S-UP3} has no effect on the expression of the Ecol\lacZ gene of P{lacZ}snunspecified or P{lacZ}vasunspecified.