The way of applying non-discrimination clauses of double taxation conventions has evolved over the years. Today, non-discrimination under tax treaties is likely to be highly influenced by developments of the non-discrimination concepts emerging from EU-community law. The Article focuses on the effects of the clause on the carry forward of losses in the case of treaties applying the exemption method and of those using the credit system. Also other implications of the clause are dealt with like the repercussion on the transformation of permanent establishments into companies, on the treatment of inter-company dividends received by permanent establishments and on the (former) possibility of deducting fictitious interest cost on equity capital; the importance of the clause for withholding tax regimes and the usage of the clause in case of third country income of permanent establishments are analysed as well.