The purpose of this study was to determine whether gingival crevicular fluid (GCF) sampling by paper strip removes sufficient bacteria to affect subsequent subgingival plaque sampling using a curette. In 25 subjects, one healthy, gingivitis and periodontitis site was sampled for GCF using a strip followed by subgingival plaque sampling with a curette. Bacterial assays indicated that GCF strips removed significant numbers of bacteria when placed intracrevicularly for 5 s. A greater proportion of total bacteria was removed with strip sampling at healthy rather than gingivitis or periodontitis sites. Qualitative assessment of presence or absence of spirochaetes and dark-pigmented species indicated potential for significant interference of curette sampling by the strip at gingivitis and healthy sites. We concluded that paper strip GCF sampling may significantly affect curette sampling at the same sites. The magnitude of this impact depended on the clinical classification of specific sites and the assay performed.