The invention relates to reagents and methods for improving the efficiency of multiplex nucleic acid amplification, in particular where overlapping amplicons are to be generated. The invention also relates to reagents and methods for improving the efficiency of multistep nucleic acid amplification, in particular the performance of two separate amplification reactions designed to occur in sequence in the same reaction mixture or vessel. The invention further relates to reagents and methods for improving multistep nucleic acid amplification reactions by controlling the output of the first amplification reaction. In particular, primers are provided that minimise the formation of aberrant amplification products. Such primers are particularly useful where first and second amplification reactions take place in a single reaction mixture or vessel.