How many times have you posted this question? I've seen it in at least two other forum sections.

In Illustrator, make a large area of your screentone pattern. Put it under your text. Select both the text and pattern and "Make Clipping Mask". (You might need to have converted the text to outlines first.)

You can do it with the screentone pattern above the text but it seems you need to make it into a Compound Path first.

I use a fairly old version of Illustrator, from CS1, so there might be other ways in newer versions.

How to make screentone pattern?? You mean to say I should manully trace it???

Take a look here.

It's basically a halftone bitmap image masked within text. To create a bitmap, open an image in Photoshop that has varying levels of gray, if it's cmyk or rgb convert it to grayscale first.

Here's how to make a halftone bitmap image.

Image>Mode>Bitmap…

Method, Use: Halftone Screen…

Adjust the Frequency, Angle and Shape to achieve the results you want. Save as a bitmap .tif or convert back to grayscale .tif then proceed to masking your type in whatever program you prefer.

What a coinkidink: Just this morning, I was noodling a project that will require a good technique for achieving this effect.

I see two solutions proposed here and in the link above, and, unfortunately for me, neither seems really elegant. One can either create a halftone in Photoshop (which leaves us with a raster image) and optionally Live Trace it in Illustrator (which leaves us with irregular shapes), or one can buy an expensive plug-in.

I don't mean to belittle the talent that goes into developing that plug-in (it looks really impressive), but the prospect of buying it for a single project isn't appealing to me.

It's unexpected and disappointing that while Photoshop has had this functionality for a long time, Illustrator still doesn't seem to. It seems like an effect that is inherently more appropriate for vector images.

Wasn't there a popular free font in the 90s that did this? It seems like there must be another way.

It seems like there must be another way.

There is:
http://typophile.com/node/80192#comment-456370

(that’s but one of the reasons it’s bad to post the same thread more than once and in different places)

One can either create a halftone in Photoshop (which leaves us with a raster image) and optionally Live Trace it in Illustrator (which leaves us with irregular shapes)

If you want your screentone vectors to be perfect circles just make them from scratch, starting with a single dot and using the Move/Copy funtion. Gradients take a bit more work as you need to keep expanding the paths on different rows.