This paper presents the first results on the preimage resistance of ISO standard hash functions RIPEMD-128 and RIPEMD-160. They were designed as strengthened versions of RIPEMD. While preimage attacks on the first 33 steps and intermediate 35 steps of RIPEMD (48 steps in total) are known, no preimage attack exists on RIPEMD-128 (64 steps) or RIPEMD-160 (80 steps). This paper shows three variations of attacks on RIPEMD-128; the first 33 steps, intermediate 35 steps, and the last 32 steps. It is interesting that the number of attacked steps for RIPEMD-128 reaches the same level as RIPEMD. We show that our approach can also be applied to RIPEMD-160, and present preimage attacks on the first 30 steps and the last 31 steps.