A solid immersion lens (SIL) has been applied to the writing and reading of three-dimensional optical data storage in transparent materials. Using a SIL with n=1.516 to focus a 150-fs, 800-nm Ti:sapphire laser, the 5-layer reading and writing of data are achieved in fused silica and polyethylene methacrylate at a density of 1.1*10^(12) b/cm3. Some advantages of the employment of SIL have been discussed.