Laser thermal balloon angioplasty was performed in 22 arteries, including iliac, superficial femoral, and popliteal arteries. The length of the lesion varied from less than two cm. to 12 cm. The yag laser was used initially, followed by conventional balloon angioplasty. Initial failure to recanalize was noted in 27 per cent, and nine per cent failed within 24 hours, i.e. a primary failure rate of 36 per cent. Initial failure was noted in 67 per cent of lesions greater than five cm. The primary failure rate was 100 per cent in lesions greater than 10 cm. and 82 per cent in lesions. Greater than five to 10 cm. There was no primary failure in lesions less than or equal to five cm. The successfully treated group (14 lesions, 65 per cent of the series), were followed three to 13 months (mean seven months) with a success rate of 86 per cent. The combined primary and secondary failure rate was 45 per cent. The overall success rate was zero per cent for lesions over five cm., and 92 per cent for lesions less than or equal to five cm. Six complications occurred (27 per cent). Two of these were major complications (nine per cent). In conclusion, the primary and secondary failure rate was unacceptable for lesions greater than five cm. LTBA probably should be confined to lesions less than or equal to five cm., and these patients should be followed closely for their long-term success. The widespread application of LTBA cannot be justified without further long-term clinical and laboratory investigation. Conversely, the potential of this technique should not be dismissed out of band.