Soft tissue sarcomas (STSs) are a heterogeneous group of rare, mesenchymal tumors. Treatment with common chemotherapeutic drugs is consistently associated with low response rates and high rates of adverse toxic effects. Host defense peptides (HDPs) are used as part of innate immunity, and many of them act by directly lysing the target cell membrane. Studies have demonstrated high selectivity of HDP analogs against malignant cells because of a relative abundance of negative charges in malignant cell membranes, compared to normal cells. Our aim was to assess the toxic efficacy of [D]-K(6)L(9), [D]-K(3)H(3)L(9), and Protegrin-1 against the fibrosarcoma cell line, HT1080, and primary human fibroblasts to analyze the potential of these peptides as therapeutic options against STSs. Cell proliferation of the fibrosarcoma cell line, HT1080, and human fibroblasts was determined in vitro after treatment with [D]-K(6)L(9), [D]-K(3)H(3)L(9), and Protegrin-1. Genotoxicity was examined on the basis of the mild alkali version of single-cell gel electrophoresis (comet assay). Doxorubicin, a commonly used STS chemotherapeutic agent, served as the control. The native HDP, Protegrin-1, could show a cytotoxic tendency against malignant cells, but no selectivity in genotoxic trials. The synthetic peptide, [D]-K(6)L(9), could not show any selective oncolytic activity against sarcoma cells. [D]-K(3)H(3)L(9) has shown a tendency for toxic selectivity against malignant cells. There is a potential of developing suitable oncolytic candidates with selectivity against malignant cells. [D]-K(3)H(3)L(9) showed the first promising results, but there has to be further investigation to improve the therapeutic properties of HDPs.