Experiments were carried out to transform laboratory mice and domestic chickens by use of sperm incubated with bacterial plasmid DNA. Following demonstration of "uptake" of such DNA by sperm of both species, attempts were made to replicate a previously published procedure (Lavitrano et al. 1989, Cell 57: 717–723) for producing transgenic mice through in vitro fertilization (IVF). Also, female mice and hens were inseminated (AI) with sperm which had been incubated in a DNA solution. Such incubation did not influence the fertility or hatchability of the hens' eggs. However, no transformed progeny were detected among 45 mice produced by IVF or among 69 mice and 470 chickens produced by AI. Key words: Sperm-mediated DNA transfer, mice, chickens