The kinetics of mobilization of hepatic and renal nickel by lipophilic drugs namely cyclam and TETA and hydrophilic drugs namely EDTA, CDTA, DTPA and HEDTA was studied at 16, 24, and 72 hrs in rats treated with nickel (II) chloride. Both the types of drugs although having comparable stability constants for nickel exhibit a marked difference in their efficacy and behaviour. The former type of drugs reduced the renal nickel while increasedits hepatic content. The latter ones reduced both renal and hepatic contents. A mathematical correlation established in the form of linear regression equations between % mobilization of nickel, stability constants and time duration revealed a positive and significant correlation between all the three parameters. These equations also revealed the highest order of efficacy of drugs at the shortest time investigated. © 1987.