favor of an actual clustering argues the geographic closeness and that some of the cases described by Halling from Södertälje (which, inciden¬ tally, does not lie in Stockholm) resembled some found in the Gothen¬ burg region. At other hospitals, although HCP had been used in many of them, pregnancy outcome agreed with that expected from the total population. Hailing finally made a study at another hospital, Karlstad, because of a supposed high use of HCP, and found a further number of malformed infants. These, however, did not resemble the malformations observed in the other two places. Hailing has formed her material of "exposed" cases by adding these three "clusters," each of which could be random. One or more of them could be due to an environmental cause. The only fact that argues in favor of this is the similarity in the malfor¬ mations observed in Gothenburg and in Södertälje, but not in Karlstad. In her "exposed" group (25 malforma¬ tions), she has thus included not only the primarily observed material (five malformations) but also a group of 15 malformations, selected as a "cluster" from a large study, which otherwise was normal. (Hailing added two cases to this material: one previous birth of an infant with Arnold-Chiari malfor¬ mation to a woman who was selected because of the birth of an anencephalic, and one case of a malformed missed abortion, which, by definition, is not an infant.) Most "exposed" cases are thus not selected because of exposure but because of the presence of malformations. It is therefore inev¬ itable that she finds a higher rate in this group than in a control group, whatever criteria she uses for its collection. According to the JAMA article, controls were selected partly from a period before "the introduc¬ tion of HCP-containing detergents in 1969." Actually, such agents were introduced and widely used in Sweden a decade earlier. The "control" group in Halling's

study comprises 233 births; malformations

were

eight

fication. When 233 randomly selected infants in Sweden are carefully stud¬ ied, one expects to find seven infants with serious malformations; if none are found, this can hardly be random (P