The effect of organic diluents on the extraction of Sr(H) from an aqueous nitrate medium (containing a mixture of 2.0 M Al(NO3)(3) + 0.5 M HNO3) using di-tert-butylcyclohexano 18 crown 6 (DTBCH18C6) as the extractant was investigated. The diluent effect on the Sr(II) transport rates across supported liquid membranes (SLM) containing DTBCH18C6/diluent as the carrier was also investigated. Though diluents containing DTBCH18C6 alone have shown moderate transport rates, their 1: 1 mixture with 1-octanol has shown significant enhancement in transport rates: a 1: 1 chloroform-octanol mixture resulted in the highest distribution ratio values though the transport rates were at maximum with a tert-butyl benzene-octanol mixture. The extractability of the metal ion was correlated with Schmidt's diluent parameter.