Omnipotent suppressors cause translational ambiguity and have been associated with poor growth and inviability. We now report that a non-Mendelian element, [eta(+)], causes this inviability. In [eta(-)] strains the suppressors are not inviable. The [eta(+)] genetic element segregates to about 70% of the meiotic progeny, although almost all of the spores probably have the [eta(+)] phenotype for the first few divisions. Growth on 5 mM guanidine hydrochloride efficiently causes [eta(+)] strains to become [eta(-)]. The [eta(+)] factor has many similarities with the previously described [psi(+)] factor (Cox 1965, 1971). However, [eta(+)] and [psi(+)] differ in their patterns of inheritance, and by the fact that [psi(+)] affects ochre specific and not omnipotent suppressors, while the converse is true of [eta(+)].