Induced pluripotent stem (iPS) cells can be derived from somatic cells by expression of specific stem cell factors and subsequently be differentiated into all cell types including cardiomyocytes. Therefore, patient-specific iPS cells could be a potent tool for the investigation of cardiac diseases in vitro, and for patient-specific high throughput drug screening. To proof the feasibility of this concept we generated iPS cells from a mouse model with long QT 3 (LQT3) syndrome carrying the deltaKPQ mutation in the SCN5A gene (SCN5Adelta). Successful reprogramming was proven by positive staining for the pluripotent markers Oct4 and SSEA1. Genotyping of isolated clones confirmed the preservation of the SCN5Adelta mutation. Patch clamp analysis of SCN5Adelta cardiomyocytes differentiated from iPS cells using the current clamp mode revealed that the action potential duration was prolonged by a reduction of the pacing rate. This typical feature of the LQT3 syndrome was not observed in wildtype cells. In addition, mutant but not wildtype cells showed the classical early after-depolarizations that are the cause for life-threatening arrhythmias in LQT3 patients. For future high throughput analyses, such as automatic planar patch clamp analysis, purified single cardiomyocytes are required. To obtain these we developed a differentiation and purification strategy using lentiviruses for genetransfer of an antibiotic resistance gene under control of the aMHC promoter. In initial experiments these purified wildtype and SCN5Adelta single cardiomyocytes were successfully used for field potential recordings in multi electrode arrays. We conclude that cardiomyocytes derived from disease-specific iPS cells can be used to recapitulate a cardiac phenotype in vitro, thus opening a new field of disease-specific pharmacological screening.