Let p be a prime number at least 5, and let k be an imaginary quadratic number field in which p decomposes into two conjugate primes. Let k ∞ be the unique Z 2 pextension of k, and let K ∞ be a finite extension of k ∞ , abelian over k. We prove that in K ∞ , the characteristic ideal of the projective limit of the p-class group coincides with the characteristic ideal of the projective limit of units modulo elliptic units. Our approach is based on Euler systems, which were first used in this context by Rubin.