The form I-600 is one of the forms available from the United States Citizenship and Immigration Services. This particular form is known as the Petition to Classify Orphan as an Immediate Relative. As the name implies, this form is specific to the classification of an alien orphan, who is under the age of 18 and who will be, or has been, adopted by a United States citizen. The adoption of this child will classify the child as an immediate relative of the United States citizen, giving them the ability to enter the United States. The petition itself is filed by the person who is adopting the child formally. Documentation must be provided showing the legal requirements and identification of the child.