B visas and B status are for visitors entering the United States temporarily for business or for pleasure.
WB status is for visitors for business who are entering the United States under the terms of the visa-waiver program , meaning that they do not have a visa stamped in their passport but are in most ways comparable to people with B-1 visas.
Similarly, WT status is for visitors for pleasure who are entering the United States under the terms of the visa-waiver program, meaning that they do not have a visa stamped in their passport but are in most ways comparable to people with B-2 visas
When is B status appropriate for a visiting foreign scholar?
A person whose primary reason for visiting the United States is a scholarly one should not enter in B-2 or WT status. B-1 status is rarely the best status for visiting scholars because of the many limitations it places on them:
WB status has all the limitations of B-1 status listed above. In addition, people in WB status cannot extend their period of stay beyond 90 days and cannot change to another status. For these reasons, J-1 status is often preferable to B-1 or WB status for visiting scholars, unless the two-year, home-country physical-presence requirement is an issue.
Can a person in B status be paid?
Yes, but not a wage or salary. A B visitor can be paid an honorarium as long as the academic activity at the UI lasts no longer than nine days and the visitor has not accepted payment or expense reimbursements from more than five other institutions or organizations in the last six months. (This is often referred to as the “9-5-6” rule.)
What are the UI procedures for paying an honorarium for a visitor in B status?
Please contact the University of Iowa Payroll Department  for procedures and information about IRS taxation rules and regulations.
How does one obtain a B visa?
Obtaining a B visa (or entering the United States in WB status) to undertake scholarly activity at the UI does not require any particular form from the UI. The visitor will want a letter on the inviting department’s letterhead giving the details of the proposed visit and activity: the dates, the activity (e.g., “give three lectures,” “perform in a recital”), and the financial terms (such as the amount of the honorarium, a statement that expenses will be reimbursed, etc.).
Of course, the scholar will have to complete the Department of State  visa application form or forms, provide photographs, and pay the visa-application fee.
How long can a person in B status remain in the United States?
At the visitor’s port of entry to the United States, the Immigration Service officer will ask about the visitor’s intentions—where she is going, what she plans to do, how long she intends to remain. The officer then authorizes a period of stay no longer than six months. People in B-1 and B-2 status can apply to the INS for extensions of the period of stay they were originally granted. People in WB status are not eligible for extensions of stay.