Repeated conjunctiva] provocation tests ICPT) were done in 20 children with rhino‐conjunctivitis due to birch pollen allergy. Compared with the first open challenge, three successive blinded CPTs were reproducible within an allergen strength difference of one 10‐potency in 92 of the tests. Based on the data, a power function was constructed, making it possible to determine the number of patients needed to discriminate CRT sensitivity of a given magnitude between two populations. During the study period specific serum‐IgE increased in only three of 19 patients, indicating that stimulation of IgE antibody production is not a common consequence of repeated tests. We conclude that CPT is useful in clinical research. When indicated in clinical routine. CPT is a sale and easy test with good prec