Lithium insertions into K+-beta-ferrite (K1.4Fe11O17) were investigated by the ion exchange in the lithium salts and by the reduction of Fe3+ in a 1.6 M solution of n-butyl-lithium (BuLi) in hexane. Li0.4K0.9Fe11O17 with beta-ferrite structure was obtained by soaking K+-beta-ferrite powder in an LiCl n-hexyl alcohol solution at 150 degrees C for 60 h. However, when the K+-beta-ferrite powders were soaked in a molten salt of LiNO3 at 270 to 310 degrees C for 20 h, the beta-structures were destroyed. It is concluded that the lithium ions can be exchanged up to 0.4 with potassium ions in the alkali layers without destruction of the beta-structure. Although the original K+-beta-ferrite maintained beta-structure at 1000 degrees C, Li0.4K0.9Fe11O17 maintained beta-structure up to 600 degrees C. On the other hand, by soaking K1.4Fe11O17 in a BuLi at 25 degrees C for 20 days, K1.2Li2.2Fe11O17 containing a large amount of lithium was obtained without destruction of the beta-structure. This structure was not destroyed by heating the K1.2Li2.2Fe11O17 at 600 degrees C. It is concluded that most of lithium ions are intercalated into the spinel blocks of beta-ferrite. The results were compared to those of the electrochemical insertion.