  SAX J1818.6-1703 has been characterised as a Supergiant Fast X-ray Transient
system on the basis of several INTEGRAL/IBIS detections since the original
BeppoSAX Wide Field Camera detection. Using IBIS/ISGRI, Swift/BAT and archival
observations, we show that in fact SAX J1818.6-1703 exhibits emission on a
period of 30 +/- 0.1 days, with a high degree of recurrence. SAX J1818.6-1703
is therefore the second SFXT shown to exhibit periodic outbursts, but with a
considerably shorter period than the other known system, IGR J11215-5952.
