An analysis of the logic of one of the commonest health beliefs in rur
al areas of Mexico is made, taking as a starting point testimonies col
lected in the area of Ocuituco, in the state of Morelos. This belief s
uggests that a pregnant woman is in danger of having a harelipped baby
during a solar eclipse. The importance of the knowledge about the log
ic of this kind of beliefs is discussed from a public health perspecti
ve. These beliefs are associated with specific forms of suffering and
give way to particular preventive measures which must be taken into ac
count if the efficacy of health programs is to be increased. The inter
relation of these beliefs with other traditional elements (such as the
''loss of the shadow'' and the ''hot-cold theory'') is discussed. Als
o, some of the already existing interpretations of this belief which s
eek to link the ''loss of the shadow'' with the solar eclipse belief a
re reviewed. Finally, an alternative interpretation of this belief is
made from a structuralist methodological perspective. This interpretat
ion is grounded in the Nahuatl myth on the creation of the sun and the
moon, and in an analysis of the nature of rabbits in the Nahuatl cult
ure, according to historic secondary sources. It is suggested that the
belief about the danger of a solar eclipse must be interpreted in con
nection to the ''hot-cold theory'', but not to the ''loss of the shado
w''. This paper concludes by emphasizing the importance of this type o
f research within the public health field, as it enables us both to un
derstand the underlying logic of this type of conceptions, and to rein
force the dialogue between modern and alternative medicine, so that th
e daily encounter between these two types of medicine can be facilitat
ed.