Adult plant testing for stripe rust resistance of spring wheat in a controlled environment was improved. By growing plants in a greenhouse under a 14/10-h light/dark cycle more vigorous plants were obtained as opposed to those grown under continuous light in a growth chamber. Ninety-eight different genotypes, with about five plants per entry, could successfully be raised in tapered plastic cones contained in a tray measuring 35 × 68 cm. The validity of testing wheat for adult plant resistance in the greenhouse was evaluated by running parallel field plots. In general, the greenhouse system accurately described field reaction types for South African, Australian and CIMMYT germplasm. A degree of underestimation of resistance occurred for some entries in the greenhouse. In a genetic study, the greenhouse and field environments differed significantly for the F₂ of a Baviaans × Avocet S cross, but not for response of F₃ families. The maximum time needed for acquiring a set of adult plant data was 8 weeks. In addition, the preconditioning of seedlings under 24 h of continuous light before inoculation produced unambiguous and consistent infection types.