Based on the classification of superregular matrices, the numbers of non-equivalent n-arcs and complete n-arcs in PG(r, q) are determined (i) for 4 q 19, 2 r q À 2 and arbitrary n, (ii) for 23 q 32, r ¼ 2 and n ! q À 8. The equivalence classes over both PGL (k, q) and PÀ ÀL(k, q) are considered throughout the examinations and computations. For the classification, an n-arc is represented by the systematic generator matrix of the corresponding MDS code, without the identity matrix part of it. A rectangular matrix like this is superregular, i.e., it has only non-singular square submatrices. Four types of superregular matrices are studied and the non-equivalent superregular matrices of different types are stored in databases. Some particular results on t(r, q) and m 0 (r, q)-the smallest and the second largest size for complete arcs in PG(r, q)-are also reported, stating that m 0 (2, 31) ¼ 22, m 0 (2, 32) ¼ 24, t(3, 23) ¼ 10, and m 0 (3, 23) ¼ 16. #