Chapter 7 - Admissions, Extensions of Stay, and Change of Status
H-3 trainees and externs should be admitted for the length of the training program, but for no longer than 2 years.  H-3 visa special education exchange visitors should be admitted for the length of the training program, but for no longer than 18 months.
H-3 trainees and special education exchange visitors who respectively, have spent 2 years or 18 months in the United States, in either H-visa or L-visa classifications may not seek extension of, change of status to, or be readmitted in, either H-visa or L-visa status unless they have resided outside the United States for the previous six months. 
There are limited exceptions to this rule. For example, the limitation does not apply to an H-3 nonimmigrant whose H or L status was seasonal, intermittent, or lasted for an aggregate of 6 months or less per year. 
Additionally, time spent as an H-4 dependent does not count against the maximum allowable periods of stay available to principals in H-3 status (or vice-versa). Thus, an alien who was previously granted H-4 dependent status and subsequently is granted H-3 classification, or an alien who was previously granted H-3 classification and subsequently is granted H-4 dependent status, may be eligible to remain in the United States for the maximum period of stay applicable to the classification.
For example, a husband and wife who come to the United States as a principal H-3 and dependent H-4 spouse may maintain status for one year, and then change status to H-4 and H-3 respectively, as long as the change of status application is properly filed before the principal H-3 has spent the maximum allowable period of stay in the United States. 
H-3 trainees and externs can only extend their stay if their original stay was less than 2 years, and the total period of stay, together with the extension period, does not exceed 2 years. H-3 special education exchange visitors can extend their stay in the United States only if their total period of stay does not exceed 18 months. 
To file for an extension, the petitioner must file another Petition for a Nonimmigrant Worker (Form I-129) and H Classification Supplement to Form I-129, fully documented in the same manner as the first petition, and also include:
A letter from the petitioner requesting an extension of status for the trainee, with an explanation of why the training has not yet been completed;
A copy of the beneficiary’s Arrival/Departure Record (Form I-94); and
A copy of the beneficiary’s first Notice of Action (Form I-797).
If the H-3 beneficiary has a dependent (a spouse, or unmarried child under the age of 21) in the United States, those dependents will need to submit an Application To Extend/Change Nonimmigrant Status (Form I-539).
Certain categories of nonimmigrants are eligible to change status to that of an H-3 nonimmigrant, including certain students and other temporary visa holders.  Such change of status requests must establish that:
The beneficiaries entered the United States legally;
The beneficiaries have never worked in the United States illegally, or otherwise violated the terms of their visa; and
The expiration date on the beneficiary’s I-94 has not passed. 
4. [^] Maintenance of H-4 status continues to be tied to the principal’s maintenance of H status. Thus, H-4 dependents may only maintain such status as long as the principal maintains the relevant principal H status.
6. [^] Certain categories generally cannot change status if they are in the United States, including nonimmigrants who entered the United States with the following visas: C, Travel without a Visa, D, K-1 or K-2, J-1, or M-1. Other nonimmigrants, such as B-1 and B-2, may change status to H-3.
7. [^] See 8 CFR 248.1(b) for information on timely filing and maintenance of status, and circumstances when failure to file timely may be excused in the discretion of USCIS.
No appendices available at this time.
Technical Update - Replacing the Term “Foreign National”October 08, 2019
This technical update replaces all instances of the term “foreign national” with “alien” throughout the Policy Manual as used to refer to a person who meets the definition provided in INA 101(a)(3) [“any person not a citizen or national of the United States”].
POLICY ALERT - Nonimmigrant Trainees (H-3)September 09, 2014
U.S. Citizenship and Immigration Services (USCIS) is issuing policy guidance on the trainees (H-3) nonimmigrant visa category.