The presence of Δ2-3 somatic transposase to Muller5-B X chromosome carrying five target P-elements causes pupal lethality, without heat shock P{A-MP1} can repress some of the lethality but heat induced expression significantly enhances repression. P{A-MP1} 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{A-MP1} cannot repress snw mutability in the male germline or the somatic instability of snw (males have patches of weak sn, extreme sn and wild-type bristles) with or without heat shock. P{A-MP1} has no effect on the expression of the Ecol\lacZ gene of P{lacZ}snunspecified or P{lacZ}vasunspecified.