Conjunctival provocation Test (CPT) is the main technique that may lead to the etiologic diagnosis of allergic conjunctivitis (AC). In most cases of seasonal and acute AC, the relationship with an allergen exposure is easily assessed. But in cases of perennial AC or in vernal as well as in atopic keratoconjunctivitis, the pertinence of the sensitization should be evidenced. To do this, CPT is the one tool available. The ophthalmologist plays a major role in its daily practice. Before CPT, a slit lamp examination is mandatory to avoid any contraindication (elevated clinical scoring, corneal impairment). The rating of symptoms occurring during CPT requires the ophthalmologist's collaboration as well as management of reactions consecutive to the instillation of increasing doses of allergens. Thus CPT requires a narrow collaboration between the ophthalmologist and the allergist.