How to render fields in form? I passed the $uid as a hook_menu()-wildcard to a form and loaded the user of that uid with $account = user_load($uid). Admin then is able to fill some textfields and save. I want some other non editable fields from $account simply to be displayed as markup or anything like that in the form. Tried to pass these fields to #markup like so:
'#markup' =&gt; $account-&gt;field.

But this doesn't work. Should this normally work? What am I doing wrong?

Or would it be better to display an aditional block which fetches the $uid from the URL and prints me my fields?
I don't see anything wrong with your approach. '#markup' =&gt; $account-&gt;field should work. Do you have it nested under a key?

$form['static_field'] = array(
    '#markup' =&gt; $account-&gt;field
);