Do you want to prove the depth of your PL/I knowledge to a prospective employer? Or do you want to verify the PL/I skills of a company to whom you might outsource your PL/I code?
The PL/I certification, developed jointly by IBM and representatives from PL/I companies from Europe and the US, can help with these and similar tasks.
At the IBM PL/I professional certification site you will find that there are two certification levels for PL/I: one for the general PL/I programmer in your team and a harder test for the leader of that PL/I team.
Check it out.