How do you populate the TextBox? Using the Text property? The Text property is a String type and the limit for a String type is around 2 billion characters so that might be the limit.
How do you append a new log line to your TextBox? Are you using the StringBuilder or just a String?
I would just keep 500 (or 1000) lines in the TextBox and then write the lod log lines to a text file.

Einar


>I am using it to log a process that is going on. It seems that after so many lines, it just stops outputting. I don't have a count though...