In the present study, anti-Leishmania immunoglobulin G (IgG) avidity was used to estimate the approximate time of disease manifestation. Significant differences (P < 0.0001) were found between the levels of anti-rKE-16 IgG avidity in leishmaniasis patients with recent and chronic diseases. More than 76% of patients with an illness duration of less than 6 months had avidity of less than 70%, 94% of patients had less than 80% avidity, and all (100%) patients with illness of more than 6 months had avidity values higher than 70%. The study showed that avidity could successfully be used to pinpoint the duration of leishmaniasis.