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Fatigue crack propagation tests with high-low and low-high blocks havebeen performed in 6082-T6 aluminium alloy at several baseline deltaK levels. The testswere carried out at constant deltaK conditions. Two stress ratios were analysed: R=0.05and R=0.4. Crack closure was monitored in all tests by the compliance technique usinga pin microgauge. The observed transient post load step behaviour is discussed in termsof the load change magnitude, deltaK baseline levels and stress ratio. The crack closureparameter U was obtained and compared with the crack growth transients. Theexperimental crack growth rate transients are compared with crack growth ratesinferred from the experimental closure measurements and the characteristic da/dNversus deltaKeff relation of the material. A good agreement between experimental andpredicted crack growth rates is obtained when the phenomenon of partial closure isproperly taken into account. Therefore, plasticity induced crack closure plays animportant role on the load interaction effects observed in aluminium alloys.