The extensive use of the combined Type A and Type B Influenza Virus Vaccine in adults has established the dosage and expected serologic response. This information is at present not available for its use in children, save for arbitrary dose schedules and one report giving such a high incidence of reactions as to contraindicate its use. The intradermal route of inoculation has been used for this vaccine in adults with satisfactory serologic response and rare reaction. The present investigation concerns the inoculation of seventy-nine children, aged one year to fourteen years, using this vaccine subcutaneously and intradermally in a variety of doses, and measuring the serologic response. The incidence of febrile reaction to subcutaneous vaccine was 59 per cent, almost all involving temperatures over 101 OF. and obvious symptoms. Following 0.1 cc. intradermally, the incidence was 26 per cent and was 36 per cent after 0.1 cc. twice, separated by three days rarely with temperatures over 101”~. and never with overt symptoms. The fold increase in antibody to Type A and Type B Influenza following 0.5 cc., 0.25 cc.and 0.125 cc. subcutaneously and .O.l cc. intradermally was equal or better than the results reported for adults. The response to 0.1 cc. intradermally given twice was most consistent and over twice the adult response. The average post-vaccination titre to the two types was as high or higher than in adults, following 0.5 cc. and 0.25 cc. subcutaneously and 0.1 cc. twice intradermally. Averaging all routes and doses, children under seven years of age had less increase and lower final titres than those over seven. The higher pre-vaccination titres yielded smaller increases in antibody. so well appreciated has been the practical aid obtained from unipolar extremity leads. A study was made in 1,000 patients of the unipolar leads with particular emphasis on their value in providing information not obtained from the standard limb and unipolar precordial leads. The findings are summarized as follows: 1. The presence of a significant Q wave in lead aVL may be the only clue to lateral myocardial infarction and indicate the advisability of high precordial leads in addition to the usual positions. The standard limb and six precordial leads may be normal or, if abnormal, of no characteristic pattern. Wilson, as well as Myers, has also called attention to the value of lead aVL . in the diagnosis of lateral myocardial infarction. 2. A study of the Q wave in lead aV, is often decisive in the interpretation of Q wave in standard lead III. In posterior myocardial infarction, the Q wave reflecting potential changes from the basal surface of the heart is transmitted to the left leg and it is only when the Q wave in III is due to a significant Q wave in aVr that the Q3 is diagnostic. 3. ST-T changes in aVL (horizontal hearts or aV, (vertical hearts) may be the first sign of left ventricular hypertrophy and may precede the ST-T abnormalities in Vg, Vs or the standard limb leads. 4. Abnormalities in lead aVr, typical of left ventricular hypertrophy or left bundle branch block may occur with normal appearing Vg and Ve if (a) the electrodes were placed too far to the right or (b) the transitional zone is displaced to the left. 5. In progressive left ventricular hypertrophy, ST-T abnormalities first appear in aVL or aVr and later in aVR. The presence of an abnormal upright T in aVR is helpful evidence of a more advanced degree of hypertrophy. 6. Questionably abnormal right and left axis deviation may be shown by unipolar limb leads to be due to marked vertical or horizontal position of the heart, and in association with the precordial leads may differentiate normal from abnormal axis deviation. 7. Unusual rotation of the heart may at times