Sergey,

>It is usefull ( generally ) only for tables with more 50% record deleted.

>That's not true. Also, with 50% or more deleted records even SEEK will take forever.

I write ( generally ), not always, and you repeat my affirmation ( for more 50% not for inferior to 50%)

I test this, and if inferior 50% records is deleted you have to build
specific index and condition for gain a big speed up.

>It slow down the insert and delete process.

>As any other index. There's nothing special aboud index on DELETED() in that regard.

It is not true.
VFP is a program at two speed:
internal speed ( C ) and language speed;
internal speed is much fast.
Then internal DELETED() test when SET DELETED is ON is faster (at least 2 X ), and the job for use a ulterior index can slow down the process.

You have to work a lot in order to find an example (not banal)
where 40% records is deleted and one query run 40% faster with one index
on DELETED().