A study seen by RTÉ Nuacht shows that not one native Irish speaker was amongst the 84 children attending naíonraí, or Irish-language preschools, in the Mayo Gaeltacht last year.
The figures also show that there were only three native Irish speakers attending naíonraí in the Kerry Gaeltacht during the school year 2004-2005.
Over half of the children in Kerry naíonraí that year had no understanding whatsoever of Irish.
The figures are stronger, however, in the Galway and Donegal Gaeltacht.
In Galway, a quarter of all children in naíonraí were native Irish speakers, although 16% had no understanding of the language.
Certain areas in Galway were stronger than others, with all children in naíonraí in An Cheathrú Rua and Inis Meáin, for example, being native speakers.
On the other hand, no child attending naíonraí east of Galway city, in Terryland and Claregalway, had any understanding of Irish.
In Donegal, two-thirds of children in naíonraí last year had at least some understanding of Irish.
A spokesperson for Comhar Naíonraí na Gaeltachta, which carried out the study and which oversees naíonra curriculum and training, said the figures follow Irish-language census patterns in the Gaeltacht.
She said, however, that it was a testament to the work of the naíonraí that most children had fluent Irish by the time they had left the naíonra and had entered the primary education system.