Abstract. We study extensions of p-local nite groups where the kernel is a pgroup. In particular, we construct examples of saturated fusion systems F which do not come from nite groups, but which have normal p-subgroups A C F such that F=A is the fusion system of a nite group. One of the tools used to do this is the concept of a \transporter system", which is modelled on the transporter category of a nite group, and is more general than a linking system.vet G e nite groupD with ylow pEsugroup S P yl p @GAF he fusion system of G @t pA is the tegory p S @GA whose ojets re the sugroups of GD nd where wor p S @GA @P; QA is the set of monomorphisms from P to Q indued y onjugtion y elements of GF he transporter system of G t p is the tegory S @GA with the sme ojets s p S @GAD nd with morphism sets wor S @GA @P; QA a N G @P; QAX the set of elements of G whih onjugte P into QF e sugroup P S is lled pEentri in G ifG @P A of order prime to pY nd the centric linking system of G is the tegory v c S @GA whose ojets re the sugroups of S whih re pEentri in GD nd where wor v c S @GA @P; QA a N G @P; QA=C H G @P AF ell of these denitions re repeted in more detil t the eginning of etion IF sn severl ppersD suh s fvyI nd yPD the fusion nd linking systems of G re shown to ply entrl role in desriing homotopy theoreti properties of the pEompleted lssifying spe BG p F estrt fusion nd linking systems hve lso een dened nd studiedD nd re shown in fvyP to hve mny of the sme properties s the fusion nd linking systems of nite groupsF e p-local nite group is dened to e triple @S; p; vAD where S is nite pEgroupD p is saturated fusion system over S @henitions IFP nd IFQAD nd v is centric linking system ssoited to p @henition IFTAF xorml nd entrl pEsugroups of fusion systems nd linking systems re lso dened @henition IFRAF gertin types of extensions of pElol nite groupsD nd in prtiulr entrl extenE sionsD were studied in fgqvyPF yne hope ws tht extensions ould provide new wy to onstrut exoti exmplesF fut in the se of entrl extensionsD this ws shown to e impossileF fy fgqvyPD heorem TFIQ nd gorollry TFIRD p=A; e v=AAF yne prolem when doing this is tht the fusion system p=A ontins too little informtionX p nnot e desried s n extension of p=A y A in ny senseF