The explosive eruption of the Indonesian island of Krakatau (Krakatoa) in 1883 almost certainly led to the total destruction of the fauna, flora and microorganisms of the three remaining islands, Rakata (Rakata Besar), Sertung and Panjang (Rakata Kecil). The Ujung Kulon peninsula of Java, 100 km to the south, was much less affected by the volcanic activity. Soil bacteria (Gram-negative rods, GNR) from Rakata (the post-1883 remnant of Krakatau) and the Ujung Kulon peninsula of Java were examined for their antibiotic-resistance patterns. A total of 27 patterns (`resistotypes') was detected, based on resistance to the antibiotics ampicillin, chloramphenicol, sulphame-thoxazole, trimethoprim, gentamicin, cephalothin and tetracycline. Nine resistotypes were common to Rakata and Java, eleven exclusive to Rakata, and seven exclusive to Java. Two of the common resistotypes (f and z) were widely distributed but most were limited in their distribution and detected at only one site. On both Java and Rakata different resistotypes were detected at different altitudes. Effective colonization of Rakata by GNR has occurred in the 101 years since its sterilization. Seeding of the upper slopes and summit of Rakata with biotypes from mountain areas in Java appears to have occurred. In addition, apparently independent evolution of GNR has occurred on Rakata. Overall, the GNR detected on the uninhabited and previously sterilized island of Rakata were resistant to as wide a range of antibiotics as were those from nearby Java.