This is happening to lots of privet hedges around the country. Sections just suddenly die. I don't know what causes it and I suspect there's not much to be done to stop it.

Others will no doubt be along soon with the proper answer

Can I ask how old it is and do you feed mulch it?

Thanks to Drc726. The privet hedge has been with us the forty years we have lived here. About twenty years ago I remember cutting it right back (what a mess it looked then!) but it grew abundantly afterwards. It does get fed indirectly from treating the beds in front with the produce of my compost bin each year.

In my 1930's house the hedge was the same age as the house, it soon re grew after a real clean out. Why not remove all the dead stuff, rubbish etc even replant the big gaps and next spring give it a good feed and mulch. Its worth a try?

I wish about 40 yards of mine would die off!!! and just leave the ones on the front of the house, my garden is next to a path through a field, and the privets slope fom about 5ft high to about 15ft at the other end, but inside is more or less level. Derek.