The　dissolution　and　growth　of　Al-3(Er,Zr)　precipitates　during　tensile　fatigue　experiments　were　investigated　by　quasi-in　situ　and　postmortem　scanning　transmission　electron　microscopy　with　Z　contrast　imaging　and　X-ray　energy　dispersive　spectroscopy.　Al-3(Er,Zr)　particles　were　observed　with　both　non-core　shell　and　core　shell　structures,　which　were　formed　during　multiple-stage　precipitations,　in　an　Al-Mg-Er　alloy.　After　fatigue　deformations,　the　average　size　of　the　non-core　shell　structured　precipitates　increased　significantly.　By　tracing　the　same　precipitate　particles　before　and　after　a　high-cycle　fatigue　test,　quasi-in　situ　electron　microscopy　revealed　that　the　increase　of　average　particle　size　is　associated　with　the　substantial　dissolution　of　small　non-core　shell　structured　Al-3(Er,Zr)　particles,　whose　diameters　are　generally　less　than　15　nm,　and　a　consequent　growth　of　larger　non-core　shell　Al-3(Er,Zr)　precipitates.　On　the　contrary,　the　core　shell　structured　Al-3(Er,Zr)　precipitates　remain　stable　during　high-cycle　fatigue　tests.　Possible　mechanisms　for　the　dissolution　and　growth　of　non-core　shell　structured　Al-3(Er,Zr)　precipitates　are　discussed　in　terms　of　particle　size,　interfacial　energy　and　lattice　mismatch,　in　comparison　to　the　stable　core　shell　structured　precipitates.　(C)　2014　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.