For an integer n ≥ 2, let NCSL(n) denote the set of sizes of congruence lattices of n-element semilattices. We find the four largest numbers belonging to NCSL(n), provided that n is large enough to ensure that |NCSL(n)| ≥ 4. Furthermore, we describe the n-element semilattices witnessing these numbers.1991 Mathematics Subject Classification. 06A12, secondary 06B10 January 4, 2018. Key words and phrases. Number of lattice congruences, size of the congruence lattice of a finite lattice, lattice with many congruences.