The seroconversion period is a time during which a person who has an infection does not test positive for it. This period occurs before a person has produced a high enough number of antibodies for a test to detect the condition.

Antibodies are proteins made by the body's natural defence system (immune system) to attack and destroy foreign substances, such as bacteria and viruses. The seroconversion period is also called the antibody development period.

The length of the seroconversion period depends on the type of infection. For example, with the human immunodeficiency virus (HIV), the seroconversion period is usually between 1 and 3 months, although it can be as short as 2 weeks or as long as 6 months. During the seroconversion period, an infected person can transmit the disease or condition even if he or she does not have signs of the infection.