The instant invention relates to a method of and an apparatus for determining a set of large sequences from an electronic data base comprising a set D={d1, . . . , dn} of transactions di (1.ltoreq.i.ltoreq.n) in a computer system with an implemented query module, each of the large sequences on the set D of transactions di having a support value greater than or equal to a given support value S, each of the transactions di of the set D being a sequence of items of a record E={e1, . . . , em} of items ej (1.ltoreq.j.ltoreq.m). A set Lk (k>2) of large sequences is determined from the set D of transactions, the large sequences of set Lk each comprising exactly k items of record E in a respective order R.sub.LK, and an associated support value S.sub.LK on the sequence D of transactions each being greater than or equal to the given support value S, and nothing but sequences comprising two of the large sequences of set Lk-1, as partly overlapping partial sequences, with the respective order R.sub.LK-1, being taken into account in determining set Lk.