Base catalysed C-C condensation reaction of intercepting carbonyl compound such as ben-zaldehyde and P- nitrobenzaldehyde with 9-chloro- and 9-bromo-fluorene was studied at dif- ferent temperatures in aqueous dioxan solution. The reaction was followed up'by a spectropho- tometric method. The order of the reaction was found to be pseudo second order. FİHBr is faster than F1HC1 by using the same aldehyde. The absorbance changes with the concentration of in» tercepting carbonyl compounds, indicating that the rate determining step involves the partici- pation of aldehyde.