Natural chemicals, vanillin and syringaldehyde were successfully condensed with resorcinol affording two different calixarenes. The ability of these calixarenes obtained from vanillin (V-host) and syringaldehyde (S-host) as the hosts for heavy metal ions (Pb2+, Ni2+, Cd2+, and Cu2+) was investigated by fluorescence studies. The results show that the fluorescence of the calixarenes was effectively quenched by adding Pb2+, particularly for S-host. The result of Stern-Volmer analysis shows a nonlinear relationship with the Pb2+ concentration. The quenching was saturated in the Pb2+ range 0.20-1.0 M, indicating the multiassociation of Pb2+ with the host. The quenching constant (Ksv) was estimated from the linear region in the range 0.25-2 mu M of Pb2+ to be 1.2 x 10(6) M-1 for the S-host and 0.22 x 106 M-1 for the V-host. Moreover, Benesi-Hildebrand analysis obtained the formation constant (K) to Pb2+ and the host, for 1.9 x 105 M-1 and 1.2 x 106 M-1 at the V- and S-host, respectively. These results indicate that Pb2+ was effectively included by the S-host.