You are basically looking for a needle in a haystack. There are thousands of white iris on the market. If I had to take shot at it, I'd say LACY SNOWFLAKE, but then again, it's anyone's guess.

Carlos

I'm hoping the size will help in Iding it. It's really tall.

Sirto, I agree with Carlos, BUT your photo is very good, especially showing us the beard colour and haft markings. You might also care to add some background details. How long have you been growing this iris? Where did you get it from? Specifically when does it bloom and how tall is it? What is the average bud count per stalk? Does it have purple based foliage? Does it increase well or poorly?
Did you ever have a label for it and lose it? (that is because the suggestion of a name may jog your memory)
Someone like Jain might be able to come up with some options, which may allow you to compare your bloom to a possible match.
I have matched irises up in this way, when I thought it would be completely hopeless. For example - My "Old Blue" which came from a friend who bought it at a nursery, who got it from a lady who used to grow lots of irises in a particular town. I took a bloom to a friend in Melbourne, and she said - That looks just like my INDIGLO which is now in bloom - come and have a look. we compared blooms - perfect match. We compared stories - hers came from a friend who bought it (with name still attached) from an elderly lady who used to grow lots of irises in a particular town! BINGO!
So you see, it can be done!

Ok, Here's the info on this iris. I bought it on Ebay last year and don't remember whether it had a name listed or not. This is the first year it is blooming. As indicated earlier it is rther tall (43 - 46" to the top of the uppermost flower)with very large flowers. There is no purple base foliage. Bud count averages 4 per stem (range of 3 to 5). First bloom was May 15th and there are about 6 of 20 buds now open.

I hope this helps narrow the field.

Yours looks something like my Renown. This picture is actually of one taken in shade, the flowers are fuller in full sun, but I didn't take a pic of those.
http://s18.photobucket