La0.7Sr0.3MnO3 nanoparticles doped with cerium (La0.7-xCe(x)Sr0.3MnO3 where 0 < or = x < or = 0.7) as well as the La(1-y)Sr(y)MnO3 nanoparticles with different values of y (La/Sr ratio) are evaluated for cytotoxicity and heating application. Considering hyperthermia as one of the possible application domains of such materials, the cytotoxicity studies were done on human skin carcinoma and human fibrosarcoma cell lines. All the samples showed the desired heating effect when subjected to high-frequency exposure at 2.45 GHz. Cytotoxicity studies revealed extremely low cytotoxicity in Ce-doped samples as well as in samples with a reduced La/Sr ratio. A maximum percentage cell viability on exposure to these nanoparticles was 95% and 85% for the two groups of samples, respectively, with a dose of 20 microg/mL for the x = 0.4 sample. The issues of dopant solubility and nonstoichiometry are discussed.