Systemic application of blackberry juice (BBJ) has a similar effect on four different skin cell lines. Immortalized cell lines (3T3 and HaCaT) and normal cell lines (normal human dermal fibroblasts and normal human epidermal keratinocytes) were treated with different doses of microfiltered and ultrafiltered BBJ (1, untreated; 2, 1:5; 3, 1:10; 4, 1:50; 5, 1:100; 6, 1:150; 7, 1:300; 8, 1:500) for 24 h, after which cells were washed once with PBS and incubated for another 24 h in fresh media (to avoid bias by cytostatic effects) and harvested. Percent cell viability was assessed by MTT assay. Data shown represent the mean ± SD of three independent experiments in which each treatment was repeated in three wells. *P ≤ 0.05 versus control.