Incorporating self-healing functionality in a polysiloxane elastomer successfully retards the growth of fatigue cracks under torsional fatigue loading. The fully in situ self-healing material consists of a microencapsulated vinyl-terminated poly(dimethylsiloxane) resin containing platinum catalyst compounds and a microencapsulated initiator (methylhydrosiloxane), embedded in a poly(dimethylsiloxane) elastomer matrix. A torsion fatigue test protocol is adopted to assess the self-healing performance of two different elastomeric matrices. Significant recovery of torsional stiffness occurs after approximately 5 h, the time required to achieve a measurable degree of cure of the healing agents. Total fatigue crack growth in a self-healing specimen is reduced by 24% in comparison to relevant controls. The retardation of growing fatigue cracks is attributed, in part, to a sliding-crack-closure mechanism, where polymerized healing agent shields the crack tip from the applied far-field stress. (c) 2008 Elsevier Ltd. All rights reserved.