Quantitative real-time polymerase chain reaction assay was used to compare the temporal transcriptional activation and mRNA removal for a number of genes in mouse embryos derived by round spermatid injection (ROSI) or intracytoplasmic sperm injection. A number of marker genes with widely different cellular functions were analyzed. Similar patterns of activation were found for the transcription factor Oct 4, the translation initiation factor eukaryotic initiation factor 1A, the L1 ribosomal protein, the chromatin modifying protein histone deacetylase 1, the enzyme hypoxanthine phosphoribosyl transferase, the murine endogenous retrovirus-like element, and the repetitive DNA LINE retrotransposons. Expression of the retrovirus-like mobile element intracisternal A particle, however, was markedly elevated from the two-cell to the blastocyst stages in ROSI embryos. Analyses performed for various paternal mRNAs introduced into the oocyte by the round spermatid, including protamines 1 and 2, transition protein 2, ropporin, and glyceraldehydes 3-phosphate dehydrogenase, revealed all were removed from the preimplantation embryos, albeit with distinct temporal patterns.