The straightforward Blaschitz et al. (2005) manuscript title makes the reader think that villous trophoblast cells in the human placenta definitely not secrete intron 4-retaining soluble HLA-G5 (also called soluble HLA-G1) molecules. Things might not be as simple… as the results presented by these authors contradict a number of previous reports on this subject (Chu et al., 1998; Solier et al., 2002; Ishitani et al., 2003; Morales et al., 2003). Rather than trying to resolve this issue, I like to focus on several experimental procedures and materials used by Blaschitz and collaborators and make the suggestion that some of them might have introduced possible biases that would possibly account for these discrepancies. Let us thus have a look at the materials and methods used by the authors.