One of to aspects of using Proc Import is to know that it is a GUESSING procedure. Depending on the file and the information/syntax that you provide to the procedure it can default to setting properties of variables after examining only a very few records. So if the first rows of a variable have the longest value of character variable of 8 characters then a longer value later in the data may only read 8 characters even when longer. You would have to show us the code, preferably from the log to show us how you imported the data.
Another bit is that small number of records might mean that the first rows examined for some variables may only have digits and be treated as numbers when later values include characters as well. Those later values would be missing.
Yet another is if you have values that consist of all digits but have leading zeroes that you need then proc import will treat the value as numeric with no leading zeroes.
If you are writing proc import code or using one of the widgets you want to set a very large number, ideally the number of rows in the file as the number to examine. This is the GUESSINGROWS option in syntax and the widget may have a box with that or a different name to place a number in.
However the leading zero issue will not be resolved by that.
