Nowadays the grid is turning into a service-oriented environment. In this context, there exist solutions to the execution of workflows and most of them are web-service based. Additionally, services are considered to exist on a .fixed host, limiting the resource alternatives when scheduling the workflow tasks. In this paper we address the problem of dynamic instantiation of grid services to schedule workflow applications. We propose an algorithm to select the best resources available to execute each task of the workflow on the already instantiated services or on services dynamically instantiated when necessary. The algorithm relies on the existence of a grid infrastructure which could provide dynamic service instantiation. Simulation results show that the scheduling algorithm associated with the dynamic service instantiation can bring more efficient workflow execution on the grid.5529 177188Forum, G.G., (2002), http://www.gridforum.org/documents/gwd-i-e/gfd-i.030.pdf, Open grid service architecture, version 1.0Huhns, M., Singh, M.P., Service-oriented computing: Key concepts and principles (2005) IEEE Internet Computing, 9 (1), pp. 75-81. , DOI 10.1109/MIC.2005.21Dasgupta, G.B., Viswanathan, B., Inform: Integrated flow orchestration and metascheduling for managed grid systems (2007) Middleware 2007: Proceedings of the 8th ACM/IFIP/USENIX international conference on Middleware, pp. 1-20. , Newport Beach, California, USAByun, E.K., Kim, J.S., (2007) Dynagrid: A dynamic service deployment and resource migration framework for WSRF-compliant applications, 33 (4-5), pp. 328-338. , Parallel ComputingQi, L., Jin, H., Foster, I., Gawor, J., Provisioning for dynamic instantiation of community services (2008) IEEE Internet Computing, 12 (2), pp. 29-36Topcuoglu, H., Hariri, S., Wu, M.-Y., Performance-effective and low-complexity task scheduling for heterogeneous computing (2002) IEEE Transactions on Parallel and Distributed Systems, 13 (3), pp. 260-274. , DOI 10.1109/71.993206Bittencourt, L.F., Madeira, E.R.M., A performance oriented adaptive scheduler for dependent tasks on grids (2008) Concurrency and Computation: Practice and Experience, 20 (9), pp. 1029-1049Senna, C.R., Madeira, E.R.M., A middleware for instrument and service orchestration in computational grids (2007) Seventh IEEE International Symposium on Cluster Computing and the Grid (CCGRID 2007), , Rio de Janeiro, Brazil. IEEE Computer Society Press, Los AlamitosEl-Rewini, H., Ali, H.H., Lewis, T.G., Task scheduling in multiprocessing systems (1995) IEEE Computer, 28 (12), pp. 27-37Wieczorek, M., Podlipnig, S., Prodan, R., Fahringer, T., Bi-criteria scheduling of scientific workflows for the grid (2008) 8th IEEE International Symposium on Cluster Computing and the Grid (CCGrid 2008), pp. 9-16. , Lyon, France IEEE Computer Society, Los AlamitosYu, J., Buyya, R., A taxonomy of scientific workflow systems for grid computing (2005) SIGMOD Record, 34 (3), pp. 44-49. , http://www.sigmod.org/sigmod/record/issues/0509/p44-special-sw-section-7. pdf, DOI 10.1145/1084805.1084814Simion, B., Leordeanu, C., Pop, F., Cristea, V., A hybrid algorithm for scheduling workflow applications in grid environments (ICPDP) (2007) OTM 2007, Part II. LNCS, 4804, pp. 1331-1348. , In: Meersman, R., Tari, Z. (eds.) Springer, HeidelbergCanon, L.C., Jeannot, E., Scheduling strategies for the bicriteria optimization of the robustness and makespan (2008) 11th International Workshop on Nature Inspired Distributed Computing (NIDISC 2008), , Miami, Florida, USA (AprilYang, T., Gerasoulis, A., Dsc: Scheduling parallel tasks on an unbounded number of processors (1994) IEEE Trans. Parallel and Distributed Systems, 5 (9), pp. 951-967Dogan, A., Özgüner, F., Biobjective scheduling algorithms for execution timereliability trade-off in heterogeneous computing systems (2005) Computer Journal, 48 (3), pp. 300-314Qi, L., Jin, H., Foster, I., Gawor, J., HAND: Highly available dynamic deployment infrastructure for globus toolkit 4 (2007) Proceedings - 15th EUROMICRO International Conference on Parallel, Distributed and Network-Based Processing, PDP 2007, pp. 155-162. , DOI 10.1109/PDP.2007.49, 4135273, Proceedings - 15th EUROMICRO International Conference on Parallel, Distributed and Network-Based Processing, PDP 2007Zeng, L., Benatallah, B., Ngu, A.H.H., Dumas, M., Kalagnanam, J., Chang, H., Qos-aware middleware for web services composition (2004) IEEE Transactions on Software Engineering, 30 (5), pp. 311-327